diff --git a/src/LibBytes.sol b/src/LibBytes.sol
index dfbe288..657f507 100644
--- a/src/LibBytes.sol
+++ b/src/LibBytes.sol
@@ -3,6 +3,7 @@ pragma solidity ^0.8.15;
 
 library LibBytes {
     function keccak(bytes memory data, uint256 offset, uint256 length) internal pure returns (bytes32 result) {
+        require(offset + length <= data.length, "index out of bounds");
         assembly {
             result := keccak256(add(data, add(32, offset)), length)
         }