diff --git a/packages/protocol/contracts/L2/TaikoL2.sol b/packages/protocol/contracts/L2/TaikoL2.sol
index f740a39a160..c024fd435c6 100644
--- a/packages/protocol/contracts/L2/TaikoL2.sol
+++ b/packages/protocol/contracts/L2/TaikoL2.sol
@@ -199,7 +199,7 @@ contract TaikoL2 is CrossChainOwned, TaikoL2Signer, ICrossChainSync {
     /// block id is greater than or equal to the current block number.
     function getBlockHash(uint64 blockId) public view returns (bytes32) {
         if (blockId >= block.number) return 0;
-        if (blockId >= block.number - 256) return blockhash(blockId);
+        if (blockId + 256 >= block.number) return blockhash(blockId);
         return l2Hashes[blockId];
     }