diff --git a/core/blockchain.go b/core/blockchain.go
index cb4bcc56ce..36187dcf86 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -1585,7 +1585,7 @@ func (bc *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 	// Do a sanity check that the provided chain is actually ordered and linked
 	for i := 1; i < len(chain); i++ {
 		block, prev := chain[i], chain[i-1]
-		if block.NumberU64() != chain[i-1].NumberU64()+1 || block.ParentHash() != chain[i-1].Hash() {
+		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
 			// Chain broke ancestry, log a messge (programming error) and skip insertion
 			log.Error("Non contiguous block insert",
 				"number", block.Number(),