diff --git a/core/block_validator.go b/core/block_validator.go
index 06410bed11..f3d65cea25 100644
--- a/core/block_validator.go
+++ b/core/block_validator.go
@@ -51,6 +51,11 @@ func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, engin
 // header's transaction and uncle roots. The headers are assumed to be already
 // validated at this point.
 func (v *BlockValidator) ValidateBody(block *types.Block) error {
+	// Check whether the block is already imported.
+	if v.bc.HasBlockAndState(block.Hash(), block.NumberU64()) {
+		return ErrKnownBlock
+	}
+
 	// Header validity is known at this point. Here we verify that uncles, transactions
 	// and withdrawals given in the block body match the header.
 	header := block.Header()