diff --git a/consensus/istanbul/backend.go b/consensus/istanbul/backend.go
index f5c23ee4c69d..94132dd4ab4a 100644
--- a/consensus/istanbul/backend.go
+++ b/consensus/istanbul/backend.go
@@ -58,9 +58,6 @@ type Backend interface {
 	// the given validator
 	CheckSignature(data []byte, addr common.Address, sig []byte) error
 
-	// GetProposer returns the proposer of the given block height
-	GetProposer(number uint64) common.Address
-
 	// LastProposal retrieves latest committed proposal and the address of proposer
 	LastProposal() (Proposal, common.Address)
 }
diff --git a/consensus/istanbul/backend/handler_test.go b/consensus/istanbul/backend/handler_test.go
index 90435b0e46f5..690a586be8f3 100644
--- a/consensus/istanbul/backend/handler_test.go
+++ b/consensus/istanbul/backend/handler_test.go
@@ -20,13 +20,9 @@ import (
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/consensus/istanbul"
-	"github.com/ethereum/go-ethereum/core/state"
-	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/rlp"
-	"github.com/ethereum/go-ethereum/rpc"
 	lru "github.com/hashicorp/golang-lru"
 )
 
@@ -74,64 +70,3 @@ func makeMsg(msgcode uint64, data interface{}) p2p.Msg {
 	size, r, _ := rlp.EncodeToReader(data)
 	return p2p.Msg{Code: msgcode, Size: uint32(size), Payload: r}
 }
-
-type MockIstanbulEngine struct{}
-
-func (m *MockIstanbulEngine) Author(header *types.Header) (common.Address, error) {
-	return common.Address{}, nil
-}
-
-func (m *MockIstanbulEngine) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
-	abort := make(chan struct{})
-	results := make(chan error, len(headers))
-	go func() {
-		for _ = range headers {
-			results <- nil
-		}
-	}()
-	return abort, results
-}
-
-func (m *MockIstanbulEngine) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) Prepare(chain consensus.ChainReader, header *types.Header) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
-	return nil, nil
-}
-
-func (m *MockIstanbulEngine) Seal(chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {
-	return nil, nil
-}
-
-func (m *MockIstanbulEngine) APIs(chain consensus.ChainReader) []rpc.API {
-	return []rpc.API{}
-}
-
-func (m *MockIstanbulEngine) HandleMsg(addr common.Address, data []byte) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) NewChainHead(block *types.Block) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) Start(chain consensus.ChainReader, inserter func(types.Blocks) (int, error)) error {
-	return nil
-}
-
-func (m *MockIstanbulEngine) Stop() error {
-	return nil
-}
diff --git a/consensus/istanbul/core/handler.go b/consensus/istanbul/core/handler.go
index 3c4cb1a3d38c..b9556b7432ef 100644
--- a/consensus/istanbul/core/handler.go
+++ b/consensus/istanbul/core/handler.go
@@ -95,11 +95,19 @@ func (c *core) handleEvents() {
 					c.storeRequestMsg(r)
 				}
 			case istanbul.MessageEvent:
-				c.handleMsg(ev.Payload)
+				if err := c.handleMsg(ev.Payload); err == nil {
+					c.backend.Gossip(c.valSet, ev.Payload)
+				}
 			case backlogEvent:
 				// No need to check signature for internal messages
-				c.handleCheckedMsg(ev.msg, ev.src)
-
+				if err := c.handleCheckedMsg(ev.msg, ev.src); err == nil {
+					p, err := ev.msg.Payload()
+					if err != nil {
+						c.logger.Warn("Get message payload failed", "err", err)
+						continue
+					}
+					c.backend.Gossip(c.valSet, p)
+				}
 			}
 		case _, ok := <-c.timeoutSub.Chan():
 			if !ok {
diff --git a/consensus/istanbul/core/preprepare.go b/consensus/istanbul/core/preprepare.go
index 7b1fcf2ecd4a..a79bfc21f97a 100644
--- a/consensus/istanbul/core/preprepare.go
+++ b/consensus/istanbul/core/preprepare.go
@@ -56,7 +56,6 @@ func (c *core) handlePreprepare(msg *message, src istanbul.Validator) error {
 	}
 
 	// Ensure we have the same view with the PRE-PREPARE message
-	// If it is old message, see if we need to broadcast COMMIT
 	if err := c.checkMessage(msgPreprepare, preprepare.View); err != nil {
 		return err
 	}
diff --git a/consensus/istanbul/core/testbackend_test.go b/consensus/istanbul/core/testbackend_test.go
index 86d9b6f74180..20fac716fe1d 100644
--- a/consensus/istanbul/core/testbackend_test.go
+++ b/consensus/istanbul/core/testbackend_test.go
@@ -138,10 +138,6 @@ func (self *testSystemBackend) NewRequest(request istanbul.Proposal) {
 	})
 }
 
-func (self *testSystemBackend) GetProposer(number uint64) common.Address {
-	return common.Address{}
-}
-
 func (self *testSystemBackend) LastProposal() (istanbul.Proposal, common.Address) {
 	return makeBlock(1), common.Address{}
 }