diff --git a/src/ets/scala/io/iohk/ethereum/ets/blockchain/BlockchainTestConfig.scala b/src/ets/scala/io/iohk/ethereum/ets/blockchain/BlockchainTestConfig.scala
index fe97161430..b8cf286ba1 100644
--- a/src/ets/scala/io/iohk/ethereum/ets/blockchain/BlockchainTestConfig.scala
+++ b/src/ets/scala/io/iohk/ethereum/ets/blockchain/BlockchainTestConfig.scala
@@ -2,7 +2,7 @@ package io.iohk.ethereum.ets.blockchain
 
 import akka.util.ByteString
 import io.iohk.ethereum.consensus.Protocol
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.domain.{Address, UInt256}
 import io.iohk.ethereum.utils.{BlockchainConfig, DaoForkConfig, MonetaryPolicyConfig}
 import org.bouncycastle.util.encoders.Hex
diff --git a/src/ets/scala/io/iohk/ethereum/ets/blockchain/ScenarioSetup.scala b/src/ets/scala/io/iohk/ethereum/ets/blockchain/ScenarioSetup.scala
index 9a7ff6fcf1..b06da2b53f 100644
--- a/src/ets/scala/io/iohk/ethereum/ets/blockchain/ScenarioSetup.scala
+++ b/src/ets/scala/io/iohk/ethereum/ets/blockchain/ScenarioSetup.scala
@@ -3,7 +3,7 @@ package io.iohk.ethereum.ets.blockchain
 import akka.util.ByteString
 import io.iohk.ethereum.consensus.Protocol.NoAdditionalEthashData
 import io.iohk.ethereum.consensus.ethash.EthashConsensus
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.consensus.{ConsensusConfig, FullConsensusConfig, TestConsensus, ethash}
 import io.iohk.ethereum.db.components.Storages.PruningModeComponent
 import io.iohk.ethereum.db.components.{EphemDataSourceComponent, Storages}
@@ -18,6 +18,7 @@ import io.iohk.ethereum.utils.BigIntExtensionMethods._
 import io.iohk.ethereum.utils.{BlockchainConfig, Config}
 import monix.execution.Scheduler
 import org.bouncycastle.util.encoders.Hex
+
 import scala.util.{Failure, Success, Try}
 
 object ScenarioSetup {
diff --git a/src/it/scala/io/iohk/ethereum/ledger/BlockImporterItSpec.scala b/src/it/scala/io/iohk/ethereum/ledger/BlockImporterItSpec.scala
index 960735af54..fe2f42e0be 100644
--- a/src/it/scala/io/iohk/ethereum/ledger/BlockImporterItSpec.scala
+++ b/src/it/scala/io/iohk/ethereum/ledger/BlockImporterItSpec.scala
@@ -8,8 +8,9 @@ import io.iohk.ethereum.blockchain.sync.regular.{BlockFetcher, BlockImporter}
 import io.iohk.ethereum.checkpointing.CheckpointingTestHelpers
 import io.iohk.ethereum.consensus.{GetBlockHeaderByHash, GetNBlocksBack}
 import io.iohk.ethereum.consensus.blocks.CheckpointBlockGenerator
-import io.iohk.ethereum.consensus.ethash.validators.{OmmersValidator, StdOmmersValidator}
+import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator
 import io.iohk.ethereum.consensus.validators.Validators
+import io.iohk.ethereum.consensus.validators.std.StdOmmersValidator
 import io.iohk.ethereum.domain._
 import io.iohk.ethereum.mpt.MerklePatriciaTrie
 import io.iohk.ethereum.utils.Config.SyncConfig
@@ -74,7 +75,7 @@ class BlockImporterItSpec
         getBlockHeaderByHash: GetBlockHeaderByHash,
         getNBlocksBack: GetNBlocksBack
     ) =>
-      new StdOmmersValidator(blockchainConfig, blockHeaderValidator)
+      new StdOmmersValidator(blockHeaderValidator)
         .validate(parentHash, blockNumber, ommers, getBlockHeaderByHash, getNBlocksBack)
   }
 
diff --git a/src/it/scala/io/iohk/ethereum/sync/RegularSyncItSpec.scala b/src/it/scala/io/iohk/ethereum/sync/RegularSyncItSpec.scala
index bddfa98dc2..44f04bc746 100644
--- a/src/it/scala/io/iohk/ethereum/sync/RegularSyncItSpec.scala
+++ b/src/it/scala/io/iohk/ethereum/sync/RegularSyncItSpec.scala
@@ -152,7 +152,12 @@ class RegularSyncItSpec extends FreeSpecBase with Matchers with BeforeAndAfterAl
       _ <- peer1.waitForRegularSyncLoadLastBlock(length)
     } yield {
       assert(peer1.bl.getBestBlock().get.hash == peer2.bl.getBestBlock().get.hash)
-      assert(peer1.bl.getBestBlock().get.number == peer2.bl.getBestBlock().get.number && peer1.bl.getBestBlock().get.number == length)
+      assert(
+        peer1.bl.getBestBlock().get.number == peer2.bl.getBestBlock().get.number && peer1.bl
+          .getBestBlock()
+          .get
+          .number == length
+      )
       assert(peer1.bl.getLatestCheckpointBlockNumber() == peer2.bl.getLatestCheckpointBlockNumber())
     }
   }
diff --git a/src/it/scala/io/iohk/ethereum/sync/util/RegularSyncItSpecUtils.scala b/src/it/scala/io/iohk/ethereum/sync/util/RegularSyncItSpecUtils.scala
index 6f4d1725c9..2bcf63fe50 100644
--- a/src/it/scala/io/iohk/ethereum/sync/util/RegularSyncItSpecUtils.scala
+++ b/src/it/scala/io/iohk/ethereum/sync/util/RegularSyncItSpecUtils.scala
@@ -7,7 +7,13 @@ import io.iohk.ethereum.Mocks.MockValidatorsAlwaysSucceed
 import io.iohk.ethereum.blockchain.sync.regular.BlockBroadcast.BlockToBroadcast
 import io.iohk.ethereum.blockchain.sync.regular.BlockBroadcasterActor.BroadcastBlock
 import io.iohk.ethereum.blockchain.sync.regular.BlockImporter.Start
-import io.iohk.ethereum.blockchain.sync.regular.{BlockBroadcast, BlockBroadcasterActor, BlockFetcher, BlockImporter, RegularSync}
+import io.iohk.ethereum.blockchain.sync.regular.{
+  BlockBroadcast,
+  BlockBroadcasterActor,
+  BlockFetcher,
+  BlockImporter,
+  RegularSync
+}
 import io.iohk.ethereum.blockchain.sync.regular.RegularSync.NewCheckpoint
 import io.iohk.ethereum.blockchain.sync.{PeersClient, SyncProtocol}
 import io.iohk.ethereum.checkpointing.CheckpointingTestHelpers
@@ -96,7 +102,8 @@ object RegularSyncItSpecUtils {
         broadcasterRef,
         pendingTransactionsManager,
         regularSync
-      ))
+      )
+    )
 
     lazy val regularSync = system.actorOf(
       RegularSync.props(
diff --git a/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcher.scala b/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcher.scala
index c034c614d7..a482739765 100644
--- a/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcher.scala
+++ b/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcher.scala
@@ -98,6 +98,7 @@ class BlockFetcher(
 
   private def handleCommands(state: BlockFetcherState): Receive = {
     case PickBlocks(amount) => state.pickBlocks(amount) |> handlePickedBlocks(state) |> fetchBlocks
+
     case StrictPickBlocks(from, atLeastWith) =>
       // FIXME: Consider having StrictPickBlocks calls guaranteeing this
       // from parameter could be negative or 0 so we should cap it to 1 if that's the case
@@ -113,6 +114,7 @@ class BlockFetcher(
       }
 
       fetchBlocks(newState)
+
     case InvalidateBlocksFrom(blockNr, reason, withBlacklist) =>
       val (blockProvider, newState) = state.invalidateBlocksFrom(blockNr, withBlacklist)
       log.debug("Invalidate blocks from {}", blockNr)
@@ -157,7 +159,7 @@ class BlockFetcher(
 
   private def handleBodiesMessages(state: BlockFetcherState): Receive = {
     case Response(peer, BlockBodies(bodies)) if state.isFetchingBodies =>
-      log.debug(s"Received ${bodies.size} block bodies")
+      log.debug("Received {} block bodies", bodies.size)
       if (state.fetchingBodiesState == AwaitingBodiesToBeIgnored) {
         log.debug("Block bodies will be ignored due to an invalidation was requested for them")
         fetchBlocks(state.withBodiesFetchReceived)
@@ -171,9 +173,10 @@ class BlockFetcher(
               state.withBodiesFetchReceived.handleRequestedBlocks(newBlocks, peer.id)
           }
         val waitingHeadersDequeued = state.waitingHeaders.size - newState.waitingHeaders.size
-        log.debug(s"Processed $waitingHeadersDequeued new blocks from received block bodies")
+        log.debug("Processed {} new blocks from received block bodies", waitingHeadersDequeued)
         fetchBlocks(newState)
       }
+
     case RetryBodiesRequest if state.isFetchingBodies =>
       log.debug("Something failed on a bodies request, cancelling the request and re-fetching")
       val newState = state.withBodiesFetchReceived
@@ -182,8 +185,10 @@ class BlockFetcher(
 
   private def handleStateNodeMessages(state: BlockFetcherState): Receive = {
     case FetchStateNode(hash) => fetchStateNode(hash, sender(), state)
+
     case RetryFetchStateNode if state.isFetchingStateNode =>
       state.stateNodeFetcher.foreach(fetcher => fetchStateNode(fetcher.hash, fetcher.replyTo, state))
+
     case Response(peer, NodeData(values)) if state.isFetchingStateNode =>
       log.debug("Received state node response from peer {}", peer)
       state.stateNodeFetcher.foreach(fetcher => {
@@ -215,10 +220,13 @@ class BlockFetcher(
       }
       supervisor ! ProgressProtocol.GotNewBlock(newState.knownTop)
       fetchBlocks(newState)
+
     case MessageFromPeer(CommonMessages.NewBlock(block, _), peerId) =>
       handleNewBlock(block, peerId, state)
+
     case MessageFromPeer(PV64.NewBlock(block, _), peerId) =>
       handleNewBlock(block, peerId, state)
+
     case BlockImportFailed(blockNr, reason) =>
       val (peerId, newState) = state.invalidateBlocksFrom(blockNr)
       peerId.foreach(id => peersClient ! BlacklistPeer(id, reason))
@@ -259,8 +267,9 @@ class BlockFetcher(
     state.tryInsertBlock(block, peerId) match {
       case Left(_) if block.number <= state.lastBlock =>
         log.debug(
-          s"Checkpoint block ${ByteStringUtils.hash2string(blockHash)} is older than current last block ${state.lastBlock}" +
-            s" - clearing the queues and putting checkpoint to ready blocks queue"
+          "Checkpoint block {} is older than current last block {} - clearing the queues and putting checkpoint to ready blocks queue",
+          ByteStringUtils.hash2string(blockHash),
+          state.lastBlock
         )
         val newState = state
           .clearQueues()
@@ -279,7 +288,7 @@ class BlockFetcher(
         log.debug(error)
         handleFutureBlock(block, state)
       case Right(state) =>
-        log.debug(s"Checkpoint block [${ByteStringUtils.hash2string(blockHash)}] fit into queues")
+        log.debug("Checkpoint block [{}] fit into queues", ByteStringUtils.hash2string(blockHash))
         fetchBlocks(state)
     }
   }
@@ -289,20 +298,20 @@ class BlockFetcher(
     //ex. After a successful handshake, fetcher will receive the info about the header of the peer best block
     case MessageFromPeer(BlockHeaders(headers), _) =>
       headers.lastOption.map { bh =>
-        log.debug(s"Candidate for new top at block ${bh.number}, current known top ${state.knownTop}")
+        log.debug("Candidate for new top at block {}, current known top {}", bh.number, state.knownTop)
         val newState = state.withPossibleNewTopAt(bh.number)
         fetchBlocks(newState)
       }
     //keep fetcher state updated in case new mined block was imported
     case InternalLastBlockImport(blockNr) =>
-      log.debug(s"New mined block $blockNr imported from the inside")
+      log.debug("New mined block {} imported from the inside", blockNr)
       val newState = state.withLastBlock(blockNr).withPossibleNewTopAt(blockNr)
 
       fetchBlocks(newState)
 
     //keep fetcher state updated in case new checkpoint block was imported
     case InternalCheckpointImport(blockNr) =>
-      log.debug(s"New checkpoint block $blockNr imported from the inside")
+      log.debug("New checkpoint block {} imported from the inside", blockNr)
 
       val newState = state
         .clearQueues()
@@ -414,13 +423,16 @@ class BlockFetcher(
 
   private def handleRequestResult(fallback: FetchMsg)(msg: Any): Task[Any] = msg match {
     case failed: RequestFailed =>
-      log.debug("Request failed due to {}", failed)
+      log.warning("Request failed due to {}", failed)
       Task.now(fallback)
+
     case NoSuitablePeer =>
       Task.now(fallback).delayExecution(syncConfig.syncRetryInterval)
+
     case Failure(cause) =>
       log.error(cause, "Unexpected error on the request result")
       Task.now(fallback)
+
     case m =>
       Task.now(m)
   }
diff --git a/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockImporter.scala b/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockImporter.scala
index 0e719638c5..cb47c625d3 100644
--- a/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockImporter.scala
+++ b/src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockImporter.scala
@@ -15,10 +15,12 @@ import io.iohk.ethereum.network.PeerId
 import io.iohk.ethereum.ommers.OmmersPool.AddOmmers
 import io.iohk.ethereum.transactions.PendingTransactionsManager
 import io.iohk.ethereum.transactions.PendingTransactionsManager.{AddUncheckedTransactions, RemoveTransactions}
+import io.iohk.ethereum.utils.ByteStringUtils
 import io.iohk.ethereum.utils.Config.SyncConfig
 import io.iohk.ethereum.utils.FunctorOps._
 import monix.eval.Task
 import monix.execution.Scheduler
+import org.bouncycastle.util.encoders.Hex
 
 import scala.concurrent.duration._
 
@@ -207,7 +209,12 @@ class BlockImporter(
             tryImportBlocks(restOfBlocks, importedBlocks)
 
           case err @ (UnknownParent | BlockImportFailed(_)) =>
-            log.error("Block {} import failed", blocks.head.number)
+            log.error(
+              "Block {} import failed, with hash {} and parent hash {}",
+              blocks.head.number,
+              blocks.head.header.hashAsHexString,
+              ByteStringUtils.hash2string(blocks.head.header.parentHash)
+            )
             Task.now((importedBlocks, Some(err)))
         }
         .onErrorHandle {
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ConsensusBuilder.scala b/src/main/scala/io/iohk/ethereum/consensus/ConsensusBuilder.scala
index f3f84622bf..1bf94498fd 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ConsensusBuilder.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/ConsensusBuilder.scala
@@ -2,7 +2,7 @@ package io.iohk.ethereum.consensus
 
 import io.iohk.ethereum.consensus.Protocol.{NoAdditionalEthashData, RestrictedEthashMinerData}
 import io.iohk.ethereum.consensus.ethash.EthashConsensus
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.nodebuilder._
 import io.iohk.ethereum.utils.{Config, Logger}
 
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/EthashConsensus.scala b/src/main/scala/io/iohk/ethereum/consensus/ethash/EthashConsensus.scala
index 1af3019a98..16e6cfe121 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/EthashConsensus.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/ethash/EthashConsensus.scala
@@ -13,8 +13,8 @@ import io.iohk.ethereum.consensus.ethash.blocks.{
   EthashBlockGeneratorImpl,
   RestrictedEthashBlockGeneratorImpl
 }
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
 import io.iohk.ethereum.consensus.validators.Validators
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.domain.BlockchainImpl
 import io.iohk.ethereum.jsonrpc.AkkaTaskOps.TaskActorOps
 import io.iohk.ethereum.ledger.BlockPreparator
@@ -22,6 +22,7 @@ import io.iohk.ethereum.ledger.Ledger.VMImpl
 import io.iohk.ethereum.nodebuilder.Node
 import io.iohk.ethereum.utils.{BlockchainConfig, Logger}
 import monix.eval.Task
+
 import scala.concurrent.duration._
 
 /**
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/EthashBlockGenerator.scala b/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/EthashBlockGenerator.scala
index cf1b908199..020d9255ee 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/EthashBlockGenerator.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/EthashBlockGenerator.scala
@@ -5,12 +5,12 @@ import akka.util.ByteString
 import io.iohk.ethereum.consensus.ConsensusConfig
 import io.iohk.ethereum.consensus.blocks._
 import io.iohk.ethereum.consensus.difficulty.DifficultyCalculator
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
 import io.iohk.ethereum.crypto.kec256
 import io.iohk.ethereum.domain._
 import io.iohk.ethereum.ledger.{BlockPreparator, InMemoryWorldStateProxy}
 import io.iohk.ethereum.utils.BlockchainConfig
 import io.iohk.ethereum.consensus.ConsensusMetrics
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 
 /** Internal API, used for testing (especially mocks) */
 trait EthashBlockGenerator extends TestBlockGenerator {
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/RestrictedEthashBlockGeneratorImpl.scala b/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/RestrictedEthashBlockGeneratorImpl.scala
index 387e54b3f5..7b8f16d0d3 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/RestrictedEthashBlockGeneratorImpl.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/RestrictedEthashBlockGeneratorImpl.scala
@@ -4,12 +4,12 @@ import io.iohk.ethereum.consensus.ConsensusConfig
 import io.iohk.ethereum.consensus.blocks.{BlockTimestampProvider, DefaultBlockTimestampProvider, PendingBlockAndState}
 import io.iohk.ethereum.consensus.difficulty.DifficultyCalculator
 import io.iohk.ethereum.consensus.ethash.RestrictedEthashSigner
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
 import io.iohk.ethereum.domain.{Address, Block, Blockchain, SignedTransaction}
 import io.iohk.ethereum.ledger.{BlockPreparator, InMemoryWorldStateProxy}
 import io.iohk.ethereum.utils.BlockchainConfig
 import org.bouncycastle.crypto.AsymmetricCipherKeyPair
 import io.iohk.ethereum.consensus.ConsensusMetrics
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 
 class RestrictedEthashBlockGeneratorImpl(
     validators: ValidatorsExecutor,
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/OmmersValidator.scala b/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/OmmersValidator.scala
index 271a6be2e8..b1aa0d838d 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/OmmersValidator.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/OmmersValidator.scala
@@ -2,6 +2,7 @@ package io.iohk.ethereum.consensus.ethash.validators
 
 import akka.util.ByteString
 import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.{OmmersError, OmmersValid}
+import io.iohk.ethereum.consensus.validators.BlockHeaderError
 import io.iohk.ethereum.consensus.{GetBlockHeaderByHash, GetNBlocksBack}
 import io.iohk.ethereum.domain.{Block, BlockHeader, Blockchain}
 
@@ -36,9 +37,10 @@ object OmmersValidator {
 
   object OmmersError {
     case object OmmersLengthError extends OmmersError
-    case object OmmersNotValidError extends OmmersError
+    case class OmmersHeaderError(errors: List[BlockHeaderError]) extends OmmersError
     case object OmmersUsedBeforeError extends OmmersError
-    case object OmmersAncestorsError extends OmmersError
+    case object OmmerIsAncestorError extends OmmersError
+    case object OmmerParentIsNotAncestorError extends OmmersError
     case object OmmersDuplicatedError extends OmmersError
   }
 
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/StdOmmersValidator.scala b/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdOmmersValidator.scala
similarity index 69%
rename from src/main/scala/io/iohk/ethereum/consensus/ethash/validators/StdOmmersValidator.scala
rename to src/main/scala/io/iohk/ethereum/consensus/validators/std/StdOmmersValidator.scala
index 5a2fd5907d..22f93a8247 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/StdOmmersValidator.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdOmmersValidator.scala
@@ -1,15 +1,14 @@
-package io.iohk.ethereum.consensus.ethash.validators
+package io.iohk.ethereum.consensus.validators.std
 
 import akka.util.ByteString
+import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator
 import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersError._
 import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.{OmmersError, OmmersValid}
-import io.iohk.ethereum.consensus.validators.BlockHeaderValidator
+import io.iohk.ethereum.consensus.validators.{BlockHeaderError, BlockHeaderValid, BlockHeaderValidator}
 import io.iohk.ethereum.consensus.{GetBlockHeaderByHash, GetNBlocksBack}
 import io.iohk.ethereum.domain.BlockHeader
-import io.iohk.ethereum.utils.BlockchainConfig
 
-class StdOmmersValidator(blockchainConfig: BlockchainConfig, blockHeaderValidator: BlockHeaderValidator)
-    extends OmmersValidator {
+class StdOmmersValidator(blockHeaderValidator: BlockHeaderValidator) extends OmmersValidator {
 
   val OmmerGenerationLimit: Int = 6 // Stated on section 11.1, eq. (143) of the YP
   val OmmerSizeLimit: Int = 2
@@ -30,7 +29,8 @@ class StdOmmersValidator(blockchainConfig: BlockchainConfig, blockHeaderValidato
     * @param getBlockHeaderByHash function to obtain an ancestor block header by hash
     * @param getNBlocksBack       function to obtain N blocks including one given by hash and its N-1 ancestors
     *
-    * @return [[OmmersValidator.OmmersValid]] if valid, an [[OmmersValidator.OmmersError]] otherwise
+    * @return [[io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersValid]] if valid,
+    *         an [[io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersError]] otherwise
     */
   def validate(
       parentHash: ByteString,
@@ -66,16 +66,21 @@ class StdOmmersValidator(blockchainConfig: BlockchainConfig, blockHeaderValidato
   /** Validates that each ommer's header is valid based on validations stated in section 11.1 of the YP
     *
     * @param ommers               the list of ommers to validate
-    * @param getBlockHeaderByHash function to obtain ommers' parents
-    *
-    * @return [[OmmersValidator.OmmersValid]] if valid, an [[OmmersValidator.OmmersError.OmmersNotValidError]] otherwise
+    * @param getBlockParentsHeaderByHash function to obtain ommers' parents
+    * @return [[OmmersValidator.OmmersValid]] if valid, an [[OmmersValidator.OmmersError.OmmersHeaderError]] otherwise
     */
   private def validateOmmersHeaders(
       ommers: Seq[BlockHeader],
-      getBlockHeaderByHash: GetBlockHeaderByHash
+      getBlockParentsHeaderByHash: GetBlockHeaderByHash
   ): Either[OmmersError, OmmersValid] = {
-    if (ommers.forall(blockHeaderValidator.validate(_, getBlockHeaderByHash).isRight)) Right(OmmersValid)
-    else Left(OmmersNotValidError)
+    val validationsResult: Seq[Either[BlockHeaderError, BlockHeaderValid]] =
+      ommers.map(blockHeaderValidator.validate(_, getBlockParentsHeaderByHash))
+
+    if (validationsResult.forall(_.isRight)) Right(OmmersValid)
+    else {
+      val errors = validationsResult.collect { case Left(error) => error }.toList
+      Left(OmmersHeaderError(errors))
+    }
   }
 
   /** Validates that each ommer is not too old and that it is a sibling as one of the current block's ancestors
@@ -85,26 +90,29 @@ class StdOmmersValidator(blockchainConfig: BlockchainConfig, blockHeaderValidato
     * @param blockNumber    the number of the block to which the ommers belong
     * @param ommers         the list of ommers to validate
     * @param getNBlocksBack from where the ommers' parents will be obtained
-    *
-    * @return [[OmmersValidator.OmmersValid]] if valid, an [[OmmersValidator.OmmersError.OmmersUsedBeforeError]] otherwise
+    * @return [[OmmersValidator.OmmersValid]] if valid, an [[OmmersValidator.OmmersError.OmmerIsAncestorError]] or
+    *         [[OmmersValidator.OmmersError.OmmerParentIsNotAncestorError]]  otherwise
     */
-  private def validateOmmersAncestors(
+  private[std] def validateOmmersAncestors(
       parentHash: ByteString,
       blockNumber: BigInt,
       ommers: Seq[BlockHeader],
       getNBlocksBack: GetNBlocksBack
   ): Either[OmmersError, OmmersValid] = {
 
-    val ancestorsOpt = collectAncestors(parentHash, blockNumber, getNBlocksBack)
+    val ancestors = collectAncestors(parentHash, blockNumber, getNBlocksBack)
+    lazy val ommersHashes: Seq[ByteString] = ommers.map(_.hash)
+    lazy val ommersThatAreAncestors: Seq[ByteString] = ancestors.map(_.hash).intersect(ommersHashes)
+
+    lazy val ancestorsParents: Seq[ByteString] = ancestors.map(_.parentHash)
+    lazy val ommersParentsHashes: Seq[ByteString] = ommers.map(_.parentHash)
+
+    // parent not an ancestor or is too old (we only compare up to 6 previous ancestors)
+    lazy val ommersParentsAreAllAncestors: Boolean = ommersParentsHashes.forall(ancestorsParents.contains)
 
-    val validOmmersAncestors: Seq[BlockHeader] => Boolean = ancestors =>
-      ommers.forall { ommer =>
-        val ommerIsNotAncestor = ancestors.forall(_.hash != ommer.hash)
-        val ommersParentIsAncestor = ancestors.exists(_.parentHash == ommer.parentHash)
-        ommerIsNotAncestor && ommersParentIsAncestor
-      }
-    if (ancestorsOpt.exists(validOmmersAncestors)) Right(OmmersValid)
-    else Left(OmmersAncestorsError)
+    if (ommersThatAreAncestors.nonEmpty) Left(OmmerIsAncestorError)
+    else if (!ommersParentsAreAllAncestors) Left(OmmerParentIsNotAncestorError)
+    else Right(OmmersValid)
   }
 
   /** Validates that each ommer was not previously used
@@ -123,9 +131,9 @@ class StdOmmersValidator(blockchainConfig: BlockchainConfig, blockHeaderValidato
       getNBlocksBack: GetNBlocksBack
   ): Either[OmmersError, OmmersValid] = {
 
-    val ommersFromAncestorsOpt = collectOmmersFromAncestors(parentHash, blockNumber, getNBlocksBack)
+    val ommersFromAncestors = collectOmmersFromAncestors(parentHash, blockNumber, getNBlocksBack)
 
-    if (ommersFromAncestorsOpt.exists(ommers.intersect(_).isEmpty)) Right(OmmersValid)
+    if (ommers.intersect(ommersFromAncestors).isEmpty) Right(OmmersValid)
     else Left(OmmersUsedBeforeError)
   }
 
@@ -144,19 +152,17 @@ class StdOmmersValidator(blockchainConfig: BlockchainConfig, blockHeaderValidato
       parentHash: ByteString,
       blockNumber: BigInt,
       getNBlocksBack: GetNBlocksBack
-  ): Option[Seq[BlockHeader]] = {
+  ): Seq[BlockHeader] = {
     val numberOfBlocks = blockNumber.min(OmmerGenerationLimit).toInt
-    val ancestors = getNBlocksBack(parentHash, numberOfBlocks).map(_.header)
-    Some(ancestors).filter(_.length == numberOfBlocks)
+    getNBlocksBack(parentHash, numberOfBlocks).map(_.header)
   }
 
   private def collectOmmersFromAncestors(
       parentHash: ByteString,
       blockNumber: BigInt,
       getNBlocksBack: GetNBlocksBack
-  ): Option[Seq[BlockHeader]] = {
+  ): Seq[BlockHeader] = {
     val numberOfBlocks = blockNumber.min(OmmerGenerationLimit).toInt
-    val ancestors = getNBlocksBack(parentHash, numberOfBlocks).map(_.body.uncleNodesList)
-    Some(ancestors).filter(_.length == numberOfBlocks).map(_.flatten)
+    getNBlocksBack(parentHash, numberOfBlocks).flatMap(_.body.uncleNodesList)
   }
 }
diff --git a/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidators.scala b/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidators.scala
index e1cf035bec..f06d9bd21f 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidators.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidators.scala
@@ -12,7 +12,7 @@ import org.bouncycastle.util.encoders.Hex
   * Implements validators that adhere to the original [[io.iohk.ethereum.consensus.validators.Validators Validators]]
   * interface.
   *
-  * @see [[io.iohk.ethereum.consensus.ethash.validators.StdValidatorsExecutor StdEthashValidators]]
+  * @see [[StdValidatorsExecutor StdEthashValidators]]
   *      for the PoW-specific counterpart.
   */
 final class StdValidators(
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/StdValidatorsExecutor.scala b/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidatorsExecutor.scala
similarity index 68%
rename from src/main/scala/io/iohk/ethereum/consensus/ethash/validators/StdValidatorsExecutor.scala
rename to src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidatorsExecutor.scala
index 4e522ac0ef..7b67bab94d 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/StdValidatorsExecutor.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/validators/std/StdValidatorsExecutor.scala
@@ -1,13 +1,14 @@
-package io.iohk.ethereum.consensus.ethash.validators
+package io.iohk.ethereum.consensus.validators.std
 
+import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator
 import io.iohk.ethereum.consensus.validators.{BlockHeaderValidator, BlockValidator, SignedTransactionValidator}
 
 /**
   * Implements validators that adhere to the PoW-specific
-  * [[io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor]]
+  * [[ValidatorsExecutor]]
   * interface.
   */
-final class StdValidatorsExecutor private[validators] (
+final class StdValidatorsExecutor private[std] (
     val blockValidator: BlockValidator,
     val blockHeaderValidator: BlockHeaderValidator,
     val signedTransactionValidator: SignedTransactionValidator,
diff --git a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/ValidatorsExecutor.scala b/src/main/scala/io/iohk/ethereum/consensus/validators/std/ValidatorsExecutor.scala
similarity index 89%
rename from src/main/scala/io/iohk/ethereum/consensus/ethash/validators/ValidatorsExecutor.scala
rename to src/main/scala/io/iohk/ethereum/consensus/validators/std/ValidatorsExecutor.scala
index cae57e80a2..f867c7e4ff 100644
--- a/src/main/scala/io/iohk/ethereum/consensus/ethash/validators/ValidatorsExecutor.scala
+++ b/src/main/scala/io/iohk/ethereum/consensus/validators/std/ValidatorsExecutor.scala
@@ -1,9 +1,14 @@
-package io.iohk.ethereum.consensus
-package ethash.validators
+package io.iohk.ethereum.consensus.validators.std
 
 import akka.util.ByteString
-import io.iohk.ethereum.consensus.validators.std.{StdBlockValidator, StdSignedTransactionValidator, StdValidators}
+import io.iohk.ethereum.consensus.ethash.validators.{
+  EthashBlockHeaderValidator,
+  MockedPowBlockHeaderValidator,
+  OmmersValidator,
+  RestrictedEthashBlockHeaderValidator
+}
 import io.iohk.ethereum.consensus.validators.{BlockHeaderValidator, Validators}
+import io.iohk.ethereum.consensus.{GetBlockHeaderByHash, GetNBlocksBack, Protocol}
 import io.iohk.ethereum.domain.{Block, Receipt}
 import io.iohk.ethereum.ledger.BlockExecutionError.ValidationBeforeExecError
 import io.iohk.ethereum.ledger.{BlockExecutionError, BlockExecutionSuccess}
@@ -55,7 +60,7 @@ object ValidatorsExecutor {
       StdBlockValidator,
       blockHeaderValidator,
       new StdSignedTransactionValidator(blockchainConfig),
-      new StdOmmersValidator(blockchainConfig, blockHeaderValidator)
+      new StdOmmersValidator(blockHeaderValidator)
     )
   }
 
@@ -66,7 +71,7 @@ object ValidatorsExecutor {
       StdBlockValidator,
       blockHeaderValidator,
       new StdSignedTransactionValidator(blockchainConfig),
-      new StdOmmersValidator(blockchainConfig, blockHeaderValidator)
+      new StdOmmersValidator(blockHeaderValidator)
     )
   }
 
diff --git a/src/main/scala/io/iohk/ethereum/domain/Blockchain.scala b/src/main/scala/io/iohk/ethereum/domain/Blockchain.scala
index 8c78bf0e3f..3fcdf1a705 100644
--- a/src/main/scala/io/iohk/ethereum/domain/Blockchain.scala
+++ b/src/main/scala/io/iohk/ethereum/domain/Blockchain.scala
@@ -446,7 +446,7 @@ class BlockchainImpl(
   private def removeBlock(block: Block, withState: Boolean): Unit = {
     val blockHash = block.hash
 
-    log.debug(s"Trying to remove block block ${block.idTag}")
+    log.debug(s"Trying to remove block ${block.idTag}")
 
     val txList = block.body.transactionList
     val bestBlockNumber = getBestBlockNumber()
diff --git a/src/main/scala/io/iohk/ethereum/ledger/BlockImport.scala b/src/main/scala/io/iohk/ethereum/ledger/BlockImport.scala
index 077e084e59..eb7339983b 100644
--- a/src/main/scala/io/iohk/ethereum/ledger/BlockImport.scala
+++ b/src/main/scala/io/iohk/ethereum/ledger/BlockImport.scala
@@ -35,7 +35,10 @@ class BlockImport(
 
     Task.parMap2(validationResult, importResult) { case (validationResult, importResult) =>
       validationResult.fold(
-        error => handleImportTopValidationError(error, block, importResult),
+        error => {
+          log.error("Error while validation block before execution: {}", error.reason)
+          handleImportTopValidationError(error, block, importResult)
+        },
         _ => importResult
       )
     }
diff --git a/src/main/scala/io/iohk/ethereum/ledger/Ledger.scala b/src/main/scala/io/iohk/ethereum/ledger/Ledger.scala
index dd063b34f5..65e4b6860f 100644
--- a/src/main/scala/io/iohk/ethereum/ledger/Ledger.scala
+++ b/src/main/scala/io/iohk/ethereum/ledger/Ledger.scala
@@ -137,13 +137,20 @@ class LedgerImpl(
               importResult.foreach(measureBlockMetrics)
               importResult
             case None =>
-              log.error(s"Getting total difficulty for current best block with hash: $hash failed")
-              Task.now(BlockImportFailed(s"Couldn't get total difficulty for current best block with hash: $hash"))
+              log.error(
+                "Getting total difficulty for current best block with hash: {} failed",
+                bestBlock.header.hashAsHexString
+              )
+              Task.now(
+                BlockImportFailed(
+                  "Couldn't get total difficulty for current best block with hash: ${bestBlock.header.hashAsHexString}"
+                )
+              )
           }
         }
       case None =>
         log.error("Getting current best block failed")
-        Task.now(BlockImportFailed(s"Couldn't find the current best block"))
+        Task.now(BlockImportFailed("Couldn't find the current best block"))
     }
 
   private def isBlockADuplicate(block: BlockHeader, currentBestBlockNumber: BigInt): Boolean = {
diff --git a/src/test/scala/io/iohk/ethereum/Mocks.scala b/src/test/scala/io/iohk/ethereum/Mocks.scala
index c2c577e4ca..c8a03d4596 100644
--- a/src/test/scala/io/iohk/ethereum/Mocks.scala
+++ b/src/test/scala/io/iohk/ethereum/Mocks.scala
@@ -2,12 +2,13 @@ package io.iohk.ethereum
 
 import akka.util.ByteString
 import cats.data.NonEmptyList
-import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersError.OmmersNotValidError
+import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersError.OmmersHeaderError
 import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersValid
-import io.iohk.ethereum.consensus.ethash.validators.{OmmersValidator, ValidatorsExecutor}
-import io.iohk.ethereum.consensus.validators.BlockHeaderError.HeaderNumberError
+import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator
+import io.iohk.ethereum.consensus.validators.BlockHeaderError.{HeaderDifficultyError, HeaderNumberError}
 import io.iohk.ethereum.consensus.validators._
 import io.iohk.ethereum.consensus.validators.std.StdBlockValidator.{BlockError, BlockTransactionsHashError, BlockValid}
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.consensus.{Consensus, GetBlockHeaderByHash, GetNBlocksBack}
 import io.iohk.ethereum.domain._
 import io.iohk.ethereum.ledger.BlockExecutionError.ValidationAfterExecError
@@ -103,7 +104,7 @@ object Mocks {
 
     override val ommersValidator: OmmersValidator =
       (_: ByteString, _: BigInt, _: Seq[BlockHeader], _: GetBlockHeaderByHash, _: GetNBlocksBack) =>
-        Left(OmmersNotValidError)
+        Left(OmmersHeaderError(List(HeaderDifficultyError)))
 
     override val blockValidator: BlockValidator = new BlockValidator {
       override def validateHeaderAndBody(blockHeader: BlockHeader, blockBody: BlockBody) = Left(
diff --git a/src/test/scala/io/iohk/ethereum/blockchain/sync/ScenarioSetup.scala b/src/test/scala/io/iohk/ethereum/blockchain/sync/ScenarioSetup.scala
index f90ca004b3..a386d86c4b 100644
--- a/src/test/scala/io/iohk/ethereum/blockchain/sync/ScenarioSetup.scala
+++ b/src/test/scala/io/iohk/ethereum/blockchain/sync/ScenarioSetup.scala
@@ -2,16 +2,18 @@ package io.iohk.ethereum.blockchain.sync
 
 import io.iohk.ethereum.Mocks
 import io.iohk.ethereum.Mocks.MockVM
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
 import io.iohk.ethereum.consensus.validators.Validators
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.consensus.{Consensus, Protocol, StdTestConsensusBuilder, TestConsensus}
 import io.iohk.ethereum.domain.BlockchainImpl
 import io.iohk.ethereum.ledger.Ledger.VMImpl
 import io.iohk.ethereum.ledger.LedgerImpl
 import io.iohk.ethereum.nodebuilder._
 import io.iohk.ethereum.utils.BlockchainConfig
+
 import java.util.concurrent.Executors
 import monix.execution.Scheduler
+
 import scala.concurrent.ExecutionContext
 
 /**
diff --git a/src/test/scala/io/iohk/ethereum/consensus/BlockGeneratorSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/blocks/BlockGeneratorSpec.scala
similarity index 99%
rename from src/test/scala/io/iohk/ethereum/consensus/BlockGeneratorSpec.scala
rename to src/test/scala/io/iohk/ethereum/consensus/blocks/BlockGeneratorSpec.scala
index 73084158ed..093e883c6e 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/BlockGeneratorSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/blocks/BlockGeneratorSpec.scala
@@ -1,11 +1,10 @@
-package io.iohk.ethereum.consensus
+package io.iohk.ethereum.consensus.blocks
 
 import akka.util.ByteString
 import io.iohk.ethereum.blockchain.data.GenesisDataLoader
 import io.iohk.ethereum.blockchain.sync.EphemBlockchainTestSetup
-import io.iohk.ethereum.consensus.blocks.BlockTimestampProvider
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
 import io.iohk.ethereum.consensus.validators._
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.crypto
 import io.iohk.ethereum.crypto._
 import io.iohk.ethereum.domain.BlockHeader.HeaderExtraFields
@@ -15,7 +14,6 @@ import io.iohk.ethereum.domain._
 import io.iohk.ethereum.ledger.{BlockExecution, BlockQueue, BlockValidation}
 import io.iohk.ethereum.mpt.MerklePatriciaTrie.MPTException
 import io.iohk.ethereum.utils._
-import java.time.Instant
 import monix.execution.Scheduler
 import org.bouncycastle.crypto.AsymmetricCipherKeyPair
 import org.bouncycastle.crypto.params.ECPublicKeyParameters
@@ -24,6 +22,8 @@ import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
 import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 
+import java.time.Instant
+
 class BlockGeneratorSpec extends AnyFlatSpec with Matchers with ScalaCheckPropertyChecks with Logger {
   implicit val testContext = Scheduler.fixedPool("block-generator-spec-pool", 4)
 
diff --git a/src/test/scala/io/iohk/ethereum/consensus/ethash/EthashMinerSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/ethash/EthashMinerSpec.scala
index ac43c9c80b..1a07ec6759 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/ethash/EthashMinerSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/ethash/EthashMinerSpec.scala
@@ -49,7 +49,8 @@ class EthashMinerSpec
 
   it should "mine valid blocks on the end of the epoch" taggedAs EthashMinerSpecTag in new TestSetup {
     val epochLength: Int = EthashUtils.EPOCH_LENGTH_BEFORE_ECIP_1099
-    val parentBlockNumber: Int = 2 * epochLength - 2 // 59998, mined block will be 59999 (last block of the current epoch)
+    val parentBlockNumber: Int =
+      2 * epochLength - 2 // 59998, mined block will be 59999 (last block of the current epoch)
     val parentBlock: Block = origin.copy(header = origin.header.copy(number = parentBlockNumber))
     val bfm: Block = blockForMining(parentBlock.header)
 
@@ -84,8 +85,9 @@ class EthashMinerSpec
       ommersPool = ommersPool.ref
     )
 
-    val miner: TestActorRef[Nothing] = TestActorRef(EthashMiner.props(blockchain, blockCreator, sync.ref, ethService, ethMiningService))
-
+    val miner: TestActorRef[Nothing] = TestActorRef(
+      EthashMiner.props(blockchain, blockCreator, sync.ref, ethService, ethMiningService)
+    )
 
     protected def executeTest(parentBlock: Block, blockForMining: Block): Unit = {
       prepareMocks(parentBlock, blockForMining)
diff --git a/src/test/scala/io/iohk/ethereum/consensus/validators/BlockHeaderValidatorSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/ethash/validators/EthashBlockHeaderValidatorSpec.scala
similarity index 99%
rename from src/test/scala/io/iohk/ethereum/consensus/validators/BlockHeaderValidatorSpec.scala
rename to src/test/scala/io/iohk/ethereum/consensus/ethash/validators/EthashBlockHeaderValidatorSpec.scala
index f930a58d26..375c75213f 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/validators/BlockHeaderValidatorSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/ethash/validators/EthashBlockHeaderValidatorSpec.scala
@@ -1,26 +1,25 @@
-package io.iohk.ethereum.consensus.validators
+package io.iohk.ethereum.consensus.ethash.validators
 
 import akka.util.ByteString
 import io.iohk.ethereum.blockchain.sync.EphemBlockchainTestSetup
 import io.iohk.ethereum.consensus.difficulty.DifficultyCalculator
 import io.iohk.ethereum.consensus.ethash.difficulty.EthashDifficultyCalculator
-import io.iohk.ethereum.consensus.ethash.validators.EthashBlockHeaderValidator
 import io.iohk.ethereum.consensus.validators.BlockHeaderError._
 import io.iohk.ethereum.consensus.validators.BlockHeaderValidator._
+import io.iohk.ethereum.consensus.validators.{BlockHeaderError, BlockHeaderValid, BlockHeaderValidatorSkeleton}
+import io.iohk.ethereum.domain.BlockHeader.HeaderExtraFields._
 import io.iohk.ethereum.domain.{UInt256, _}
 import io.iohk.ethereum.utils.{BlockchainConfig, DaoForkConfig}
-import io.iohk.ethereum.{Fixtures, ObjectGenerators}
+import io.iohk.ethereum.{Fixtures, ObjectGenerators, SuperSlow}
 import org.bouncycastle.util.encoders.Hex
 import org.scalamock.scalatest.MockFactory
-import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
-import io.iohk.ethereum.domain.BlockHeader.HeaderExtraFields._
-import io.iohk.ethereum.SuperSlow
 import org.scalatest.prop.TableFor4
+import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 
 // scalastyle:off magic.number
-class BlockHeaderValidatorSpec
+class EthashBlockHeaderValidatorSpec
     extends AnyFlatSpec
     with Matchers
     with ScalaCheckPropertyChecks
diff --git a/src/test/scala/io/iohk/ethereum/consensus/validators/RestrictedEthashBlockHeaderValidatorSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/ethash/validators/RestrictedEthashBlockHeaderValidatorSpec.scala
similarity index 98%
rename from src/test/scala/io/iohk/ethereum/consensus/validators/RestrictedEthashBlockHeaderValidatorSpec.scala
rename to src/test/scala/io/iohk/ethereum/consensus/ethash/validators/RestrictedEthashBlockHeaderValidatorSpec.scala
index 770e3a2c1d..c5c37e024e 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/validators/RestrictedEthashBlockHeaderValidatorSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/ethash/validators/RestrictedEthashBlockHeaderValidatorSpec.scala
@@ -1,9 +1,9 @@
-package io.iohk.ethereum.consensus.validators
+package io.iohk.ethereum.consensus.ethash.validators
 
 import akka.util.ByteString
 import io.iohk.ethereum.consensus.ethash.RestrictedEthashSigner
-import io.iohk.ethereum.consensus.ethash.validators.RestrictedEthashBlockHeaderValidator
 import io.iohk.ethereum.consensus.validators.BlockHeaderError.{HeaderPoWError, RestrictedEthashHeaderExtraDataError}
+import io.iohk.ethereum.consensus.validators.BlockHeaderValid
 import io.iohk.ethereum.crypto
 import io.iohk.ethereum.crypto.ECDSASignature
 import io.iohk.ethereum.domain.{Address, BlockHeader, UInt256}
diff --git a/src/test/scala/io/iohk/ethereum/consensus/validators/BlockValidatorSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/validators/std/StdBlockValidatorSpec.scala
similarity index 97%
rename from src/test/scala/io/iohk/ethereum/consensus/validators/BlockValidatorSpec.scala
rename to src/test/scala/io/iohk/ethereum/consensus/validators/std/StdBlockValidatorSpec.scala
index ad6b473590..759521c824 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/validators/BlockValidatorSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/validators/std/StdBlockValidatorSpec.scala
@@ -1,19 +1,18 @@
-package io.iohk.ethereum.consensus.validators
+package io.iohk.ethereum.consensus.validators.std
 
 import akka.util.ByteString
 import io.iohk.ethereum.checkpointing.CheckpointingTestHelpers
 import io.iohk.ethereum.consensus.blocks.CheckpointBlockGenerator
-import io.iohk.ethereum.consensus.validators.std.StdBlockValidator
 import io.iohk.ethereum.consensus.validators.std.StdBlockValidator._
 import io.iohk.ethereum.crypto
 import io.iohk.ethereum.domain._
-import io.iohk.ethereum.security.SecureRandomBuilder
 import io.iohk.ethereum.ledger.BloomFilter
+import io.iohk.ethereum.security.SecureRandomBuilder
 import org.bouncycastle.util.encoders.Hex
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
 
-class BlockValidatorSpec extends AnyFlatSpec with Matchers with SecureRandomBuilder {
+class StdBlockValidatorSpec extends AnyFlatSpec with Matchers with SecureRandomBuilder {
 
   "Block" should "created based on valid data" in {
     val block = Block(validBlockHeader, validBlockBody)
diff --git a/src/test/scala/io/iohk/ethereum/consensus/validators/OmmersValidatorSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/validators/std/StdOmmersValidatorSpec.scala
similarity index 86%
rename from src/test/scala/io/iohk/ethereum/consensus/validators/OmmersValidatorSpec.scala
rename to src/test/scala/io/iohk/ethereum/consensus/validators/std/StdOmmersValidatorSpec.scala
index 11de518411..b190d2750c 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/validators/OmmersValidatorSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/validators/std/StdOmmersValidatorSpec.scala
@@ -1,17 +1,17 @@
-package io.iohk.ethereum.consensus.validators
+package io.iohk.ethereum.consensus.validators.std
 
 import akka.util.ByteString
 import io.iohk.ethereum.ObjectGenerators
 import io.iohk.ethereum.blockchain.sync.EphemBlockchainTestSetup
+import io.iohk.ethereum.consensus.ethash.validators.EthashBlockHeaderValidator
 import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator.OmmersError._
-import io.iohk.ethereum.consensus.ethash.validators.{EthashBlockHeaderValidator, StdOmmersValidator}
 import io.iohk.ethereum.domain.{Block, BlockBody, BlockHeader}
 import org.bouncycastle.util.encoders.Hex
-import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
+import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
 
-class OmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPropertyChecks with ObjectGenerators {
+class StdOmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPropertyChecks with ObjectGenerators {
 
   it should "validate correctly a valid list of ommers" in new BlockUtils {
     ommersValidator.validate(ommersBlockParentHash, ommersBlockNumber, ommers, blockchain) match {
@@ -20,7 +20,7 @@ class OmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPrope
     }
   }
 
-  it should "report a failure if the list of ommers is too big" in new BlockUtils {
+  it should "report failure if the list of ommers is too big" in new BlockUtils {
     ommersValidator.validate(ommersBlockParentHash, ommersBlockNumber, Seq(ommer1, ommer2, ommer2), blockchain) match {
       case Left(OmmersLengthError) => succeed
       case Left(err) => fail(s"Unexpected validation error: $err")
@@ -28,17 +28,17 @@ class OmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPrope
     }
   }
 
-  it should "report a failure if there is an invalid header in the list of ommers" in new BlockUtils {
+  it should "report failure if there is an invalid header in the list of ommers" in new BlockUtils {
     val invalidOmmer1: BlockHeader = ommer1.copy(number = ommer1.number + 1)
 
     ommersValidator.validate(ommersBlockParentHash, ommersBlockNumber, Seq(invalidOmmer1, ommer2), blockchain) match {
-      case Left(OmmersNotValidError) => succeed
+      case Left(OmmersHeaderError(List(_))) => succeed
       case Left(err) => fail(s"Unexpected validation error: $err")
       case Right(_) => fail("Unexpected validation success")
     }
   }
 
-  it should "report a failure if there is an ommer that was previously used" in new BlockUtils {
+  it should "report failure if there is an ommer that was previously used" in new BlockUtils {
     ommersValidator.validate(
       ommersBlockParentHash,
       ommersBlockNumber,
@@ -51,22 +51,51 @@ class OmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPrope
     }
   }
 
-  it should "report a failure if there is an ommer which is of the last ancestors" in new BlockUtils {
+  it should "report failure if there is an ommer which is also an ancestor" in new BlockUtils {
     ommersValidator.validate(ommersBlockParentHash, ommersBlockNumber, Seq(ommer1, block92.header), blockchain) match {
-      case Left(OmmersAncestorsError) => succeed
+      case Left(OmmerIsAncestorError) => succeed
       case Left(err) => fail(s"Unexpected validation error: $err")
       case Right(_) => fail("Unexpected validation success")
     }
   }
 
-  it should "report a failure if there is an ommer too old" in new BlockUtils {
+  it should "report failure if there is an ommer which that is not parent of an ancestor" in new BlockUtils {
+    val getNBlocksBack: (ByteString, Int) => List[Block] =
+      (_, n) => ((ommersBlockNumber - n) until ommersBlockNumber).toList.flatMap(blockchain.getBlockByNumber)
+
+    ommersValidator.validateOmmersAncestors(
+      ommersBlockParentHash,
+      ommersBlockNumber,
+      Seq(ommer1, ommerInvalidBranch),
+      getNBlocksBack
+    ) match {
+      case Left(OmmerParentIsNotAncestorError) => succeed
+      case err => fail(err.toString)
+    }
+  }
+
+  it should "report failure if getNBlocksBack returns an empty list of ancestors" in new BlockUtils {
+    val getNBlocksBack: (ByteString, Int) => List[Block] = (_, _) => List.empty
+
+    ommersValidator.validateOmmersAncestors(
+      ommersBlockParentHash,
+      ommersBlockNumber,
+      Seq(ommer1, ommerInvalidBranch),
+      getNBlocksBack
+    ) match {
+      case Left(OmmerParentIsNotAncestorError) => succeed
+      case err => fail(err.toString)
+    }
+  }
+
+  it should "report failure if there is an ommer that is too old" in new BlockUtils {
     ommersValidator.validate(ommersBlockParentHash, ommersBlockNumber, Seq(ommer1, block90.header), blockchain) match {
-      case Left(OmmersAncestorsError) => succeed
-      case _ => fail()
+      case Left(OmmerParentIsNotAncestorError) => succeed
+      case err => fail(err.toString)
     }
   }
 
-  it should "report a failure if there is a duplicated ommer in the ommer list" in new BlockUtils {
+  it should "report failure if there is a duplicated ommer in the ommers list" in new BlockUtils {
     ommersValidator.validate(ommersBlockParentHash, ommersBlockNumber, Seq(ommer1, ommer1), blockchain) match {
       case Left(OmmersDuplicatedError) => succeed
       case Left(err) => fail(s"Unexpected validation error: $err")
@@ -77,7 +106,29 @@ class OmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPrope
   // scalastyle:off magic.number
   trait BlockUtils extends EphemBlockchainTestSetup {
 
-    val ommersValidator = new StdOmmersValidator(blockchainConfig, new EthashBlockHeaderValidator(blockchainConfig))
+    val ommersValidator = new StdOmmersValidator(new EthashBlockHeaderValidator(blockchainConfig))
+
+    val ommerInvalidBranch = BlockHeader(
+      parentHash = ByteString(Hex.decode("fd07e36cfaf327801e5696134b12345f6a89fb1e8f017f2411a29d0ae810ab8b")),
+      ommersHash = ByteString(Hex.decode("7766c4251396a6833ccbe4be86fbda3a200dccbe6a15d80ae3de5378b1540e04")),
+      beneficiary = ByteString(Hex.decode("28921e4e2c9d84f4c0f0c0ceb991f45751a0fe93")),
+      stateRoot = ByteString(Hex.decode("e766f9c51536e9038849e5eb0a143c3b3409b5385098359837cbf3324ad22328")),
+      transactionsRoot = ByteString(Hex.decode("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")),
+      receiptsRoot = ByteString(Hex.decode("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")),
+      logsBloom = ByteString(
+        Hex.decode(
+          "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        )
+      ),
+      difficulty = BigInt("17864037202"),
+      number = 94,
+      gasLimit = 5000,
+      gasUsed = 0,
+      unixTimestamp = 1438270431,
+      extraData = ByteString(Hex.decode("476574682f76312e302e302f6c696e75782f676f312e342e32")),
+      mixHash = ByteString(Hex.decode("8c1ed8037984be0fe9065f8f8663c3baeeb6436868ac6915dd3c2cd5fd46fa96")),
+      nonce = ByteString(Hex.decode("40b0b2c0b6d14706"))
+    )
 
     //Ommers from block 0xe9fb121a7ee5cb03b33adbf59e95321a2453f09db98068e1f31f0da79860c50c (of number 97)
     val ommer1 = BlockHeader(
@@ -123,7 +174,7 @@ class OmmersValidatorSpec extends AnyFlatSpec with Matchers with ScalaCheckPrope
       nonce = ByteString(Hex.decode("40b0b2c0b6d14706"))
     )
     val ommers: Seq[BlockHeader] = Seq[BlockHeader](ommer1, ommer2)
-    val ommersBlockNumber = 97
+    val ommersBlockNumber: BigInt = 97
 
     val block90 = Block(
       BlockHeader(
diff --git a/src/test/scala/io/iohk/ethereum/consensus/validators/SignedTransactionValidatorSpec.scala b/src/test/scala/io/iohk/ethereum/consensus/validators/std/StdSignedTransactionValidatorSpec.scala
similarity index 98%
rename from src/test/scala/io/iohk/ethereum/consensus/validators/SignedTransactionValidatorSpec.scala
rename to src/test/scala/io/iohk/ethereum/consensus/validators/std/StdSignedTransactionValidatorSpec.scala
index 974bdf9b94..6258beafb7 100644
--- a/src/test/scala/io/iohk/ethereum/consensus/validators/SignedTransactionValidatorSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/consensus/validators/std/StdSignedTransactionValidatorSpec.scala
@@ -1,11 +1,8 @@
-package io.iohk.ethereum.consensus.validators
-
-import java.math.BigInteger
-import java.security.SecureRandom
+package io.iohk.ethereum.consensus.validators.std
 
 import akka.util.ByteString
 import io.iohk.ethereum.consensus.validators.SignedTransactionError.{TransactionSignatureError, _}
-import io.iohk.ethereum.consensus.validators.std.StdSignedTransactionValidator
+import io.iohk.ethereum.consensus.validators.{SignedTransactionError, SignedTransactionValid}
 import io.iohk.ethereum.crypto.ECDSASignature
 import io.iohk.ethereum.domain._
 import io.iohk.ethereum.utils.Config
@@ -15,7 +12,10 @@ import org.bouncycastle.util.encoders.Hex
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
 
-class SignedTransactionValidatorSpec extends AnyFlatSpec with Matchers {
+import java.math.BigInteger
+import java.security.SecureRandom
+
+class StdSignedTransactionValidatorSpec extends AnyFlatSpec with Matchers {
 
   val blockchainConfig = Config.blockchains.blockchainConfig
 
diff --git a/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingJRCSpec.scala b/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingJRCSpec.scala
index 84d5128718..8dc965d20d 100644
--- a/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingJRCSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingJRCSpec.scala
@@ -41,7 +41,8 @@ class CheckpointingJRCSpec
       "block" -> JObject(
         "hash" -> JString("0x" + ByteStringUtils.hash2string(block.hash)),
         "number" -> JInt(block.number)
-    ))
+      )
+    )
 
     val response = jsonRpcController.handleRequest(request).runSyncUnsafe()
     response should haveResult(expectedResult)
diff --git a/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingServiceSpec.scala b/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingServiceSpec.scala
index b93ddabae2..d4ba3be3f8 100644
--- a/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingServiceSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/jsonrpc/CheckpointingServiceSpec.scala
@@ -96,7 +96,9 @@ class CheckpointingServiceSpec
       val expectedResponse = GetLatestBlockResponse(None)
 
       (blockchain.getBestBlockNumber _).expects().returning(bestBlockNum)
-      (blockchain.getBlockHeaderByHash _).expects(hash).returning(Some(previousCheckpoint.header.copy(number = bestBlockNum)))
+      (blockchain.getBlockHeaderByHash _)
+        .expects(hash)
+        .returning(Some(previousCheckpoint.header.copy(number = bestBlockNum)))
       (blockchain.getBlockByNumber _).expects(*).returning(Some(previousCheckpoint))
       val result = service.getLatestBlock(request)
 
diff --git a/src/test/scala/io/iohk/ethereum/jsonrpc/JsonRpcControllerFixture.scala b/src/test/scala/io/iohk/ethereum/jsonrpc/JsonRpcControllerFixture.scala
index cfdc4f556d..16157feaae 100644
--- a/src/test/scala/io/iohk/ethereum/jsonrpc/JsonRpcControllerFixture.scala
+++ b/src/test/scala/io/iohk/ethereum/jsonrpc/JsonRpcControllerFixture.scala
@@ -6,7 +6,7 @@ import akka.util.ByteString
 import io.iohk.ethereum.blockchain.sync.EphemBlockchainTestSetup
 import io.iohk.ethereum.consensus.blocks.CheckpointBlockGenerator
 import io.iohk.ethereum.consensus.ethash.blocks.EthashBlockGenerator
-import io.iohk.ethereum.consensus.ethash.validators.ValidatorsExecutor
+import io.iohk.ethereum.consensus.validators.std.ValidatorsExecutor
 import io.iohk.ethereum.consensus.{ConsensusConfigs, TestConsensus}
 import io.iohk.ethereum.crypto.ECDSASignature
 import io.iohk.ethereum.db.storage.AppStateStorage
diff --git a/src/test/scala/io/iohk/ethereum/ledger/LedgerTestSetup.scala b/src/test/scala/io/iohk/ethereum/ledger/LedgerTestSetup.scala
index 4999d3fb00..629c591445 100644
--- a/src/test/scala/io/iohk/ethereum/ledger/LedgerTestSetup.scala
+++ b/src/test/scala/io/iohk/ethereum/ledger/LedgerTestSetup.scala
@@ -5,8 +5,9 @@ import akka.util.ByteString.{empty => bEmpty}
 import cats.data.NonEmptyList
 import io.iohk.ethereum.blockchain.sync.EphemBlockchainTestSetup
 import io.iohk.ethereum.consensus.blocks.CheckpointBlockGenerator
-import io.iohk.ethereum.consensus.ethash.validators.{OmmersValidator, StdOmmersValidator}
+import io.iohk.ethereum.consensus.ethash.validators.OmmersValidator
 import io.iohk.ethereum.consensus.validators.BlockHeaderError.HeaderParentNotFoundError
+import io.iohk.ethereum.consensus.validators.std.StdOmmersValidator
 import io.iohk.ethereum.consensus.validators.{BlockHeaderError, BlockHeaderValid, BlockHeaderValidator, Validators}
 import io.iohk.ethereum.consensus.{GetBlockHeaderByHash, GetNBlocksBack, TestConsensus}
 import io.iohk.ethereum.crypto.{generateKeyPair, kec256}
@@ -434,7 +435,7 @@ trait OmmersTestSetup extends EphemBlockchain {
         getBlockHeaderByHash: GetBlockHeaderByHash,
         getNBlocksBack: GetNBlocksBack
     ) =>
-      new StdOmmersValidator(blockchainConfig, blockHeaderValidator)
+      new StdOmmersValidator(blockHeaderValidator)
         .validate(parentHash, blockNumber, ommers, getBlockHeaderByHash, getNBlocksBack)
   }
 
diff --git a/src/test/scala/io/iohk/ethereum/network/handshaker/EtcHandshakerSpec.scala b/src/test/scala/io/iohk/ethereum/network/handshaker/EtcHandshakerSpec.scala
index 039d639745..a7f11a712c 100644
--- a/src/test/scala/io/iohk/ethereum/network/handshaker/EtcHandshakerSpec.scala
+++ b/src/test/scala/io/iohk/ethereum/network/handshaker/EtcHandshakerSpec.scala
@@ -269,8 +269,7 @@ class EtcHandshakerSpec extends AnyFlatSpec with Matchers {
     )
     lazy val nodeStatusHolder = new AtomicReference(nodeStatus)
 
-    class MockEtcHandshakerConfiguration(pv: Int = Config.Network.protocolVersion)
-        extends EtcHandshakerConfiguration {
+    class MockEtcHandshakerConfiguration(pv: Int = Config.Network.protocolVersion) extends EtcHandshakerConfiguration {
       override val forkResolverOpt: Option[ForkResolver] = None
       override val nodeStatusHolder: AtomicReference[NodeStatus] = TestSetup.this.nodeStatusHolder
       override val peerConfiguration: PeerConfiguration = Config.Network.peer