diff --git a/core/blockchain.go b/core/blockchain.go
index 156efe303a..df20998ba4 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -65,7 +65,12 @@ const (
 	triesInMemory       = 128
 
 	// BlockChainVersion ensures that an incompatible database forces a resync from scratch.
-	BlockChainVersion uint64 = 3
+	//
+	// During the process of upgrading the database version from 3 to 4,
+	// the following incompatible database changes were added.
+	// * the `BlockNumber`, `TxHash`, `TxIndex`, `BlockHash` and `Index` fields of log are deleted
+	// * the `Bloom` field of receipt is deleted
+	BlockChainVersion uint64 = 4
 )
 
 // CacheConfig contains the configuration values for the trie caching/pruning