diff --git a/libraries/app/application.cpp b/libraries/app/application.cpp
index 4a965d6bbc..b260f1af24 100644
--- a/libraries/app/application.cpp
+++ b/libraries/app/application.cpp
@@ -523,9 +523,9 @@ namespace detail {
 
       bool is_included_block(const block_id_type& block_id)
       {
-        uint32_t block_num = block_header::num_from_id(block_id);
-        block_id_type block_id_in_preferred_chain = _chain_db->get_block_id_for_num(block_num);
-        return block_id == block_id_in_preferred_chain;
+         uint32_t block_num = block_header::num_from_id(block_id);
+         block_id_type block_id_in_preferred_chain = _chain_db->get_block_id_for_num(block_num);
+         return block_id == block_id_in_preferred_chain;
       }
 
       /**
diff --git a/libraries/chain/block_log.cpp b/libraries/chain/block_log.cpp
index 507ffd7881..a49d29786e 100644
--- a/libraries/chain/block_log.cpp
+++ b/libraries/chain/block_log.cpp
@@ -172,16 +172,23 @@ namespace steemit { namespace chain {
 
    uint64_t block_log::append( const signed_block& b )
    {
-      my->check_block_write();
-      my->check_index_write();
-
-      uint64_t pos = my->block_stream.tellp();
-      fc::raw::pack( my->block_stream, b );
-      my->block_stream.write( (char*)&pos, sizeof( pos ) );
-      my->index_stream.write( (char*)&pos, sizeof( pos ) );
-      my->head = b;
-      my->head_id = b.id();
-      return pos;
+      try
+      {
+         my->check_block_write();
+         my->check_index_write();
+
+         uint64_t pos = my->block_stream.tellp();
+         FC_ASSERT( my->index_stream.tellp() == sizeof( uint64_t ) * ( b.block_num() - 1 ), "Append to index file occuring at wrong position.", ( "position", (uint64_t) my->index_stream.tellp() )( "expected",( b.block_num() - 1 ) * sizeof( uint64_t ) ) );
+         auto data = fc::raw::pack( b );
+         my->block_stream.write( data.data(), data.size() );
+         my->block_stream.write( (char*)&pos, sizeof( pos ) );
+         my->index_stream.write( (char*)&pos, sizeof( pos ) );
+         my->head = b;
+         my->head_id = b.id();
+
+         return pos;
+      }
+      FC_LOG_AND_RETHROW()
    }
 
    void block_log::flush()
@@ -208,7 +215,10 @@ namespace steemit { namespace chain {
       optional< signed_block > b;
       uint64_t pos = get_block_pos( block_num );
       if( pos != npos )
+      {
          b = read_block( pos ).first;
+         FC_ASSERT( b->block_num() == block_num , "Wrong block was read from block log.", ( "returned", b->block_num() )( "expected", block_num ));
+      }
       return b;
       }
       FC_LOG_AND_RETHROW()