diff --git a/tests/regression/foundry.toml b/tests/regression/foundry.toml
index 57071666..fb46a974 100644
--- a/tests/regression/foundry.toml
+++ b/tests/regression/foundry.toml
@@ -5,6 +5,8 @@ libs = ['../lib', 'lib']
 
 evm_version = 'cancun'
 
+optimizer = true
+
 force = false
 # compile options used by halmos (to prevent unnecessary recompilation when running forge test and halmos together)
 extra_output = ["storageLayout", "metadata"]
diff --git a/tests/regression/test/MegaMem.t.sol b/tests/regression/test/MegaMem.t.sol
index a4bfb8ab..2657d5ee 100644
--- a/tests/regression/test/MegaMem.t.sol
+++ b/tests/regression/test/MegaMem.t.sol
@@ -76,10 +76,13 @@ contract MegaMemTest is Test, SymTest {
         }
     }
 
-    function keccak256_op(uint256 ptr, uint256 len) public pure {
+
+    function keccak256_op(uint256 ptr, uint256 len) public pure returns (bytes32) {
+        bytes32 hash;
         assembly {
-            let hash := keccak256(ptr, len)
+            hash := keccak256(ptr, len)
         }
+        return hash;
     }
 
     function mcopy(uint256 dst_ptr, uint256 src_ptr, uint256 src_len) public pure {