diff --git a/core/types/block.go b/core/types/block.go
index 92b868d9da..ab1716fdf0 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -100,6 +100,14 @@ type headerMarshaling struct {
 // Hash returns the block hash of the header, which is simply the keccak256 hash of its
 // RLP encoding.
 func (h *Header) Hash() common.Hash {
+	// If the mix digest is equivalent to the predefined Istanbul digest, use Istanbul
+	// specific hash calculation.
+	//if h.MixDigest == IstanbulDigest {
+	//	// Seal is reserved in extra-data. To prove block is signed by the proposer.
+	//	if istanbulHeader := IstanbulFilteredHeader(h, true); istanbulHeader != nil {
+	//		return rlpHash(istanbulHeader)
+	//	}
+	//}
 	return rlpHash(h)
 }