diff --git a/.gas-snapshot b/.gas-snapshot
index 251f9f580..33613b6b5 100644
--- a/.gas-snapshot
+++ b/.gas-snapshot
@@ -12,12 +12,12 @@ Base64Test:testBase64EncodeToStringWithSinglePadding() (gas: 1636)
 Base64Test:testBase64WordBoundary() (gas: 12511)
 Base64Test:test__codesize() (gas: 7857)
 CREATE3Test:testDeployERC20() (gas: 800066)
-CREATE3Test:testDeployERC20(bytes32,string,string,uint8) (runs: 256, μ: 870427, ~: 869184)
+CREATE3Test:testDeployERC20(bytes32,string,string,uint8) (runs: 256, μ: 871887, ~: 869184)
 CREATE3Test:testDeployedUpperBitsSafeForPlainSolidity() (gas: 609)
 CREATE3Test:testDoubleDeployDifferentBytecodeReverts() (gas: 96901099)
-CREATE3Test:testDoubleDeployDifferentBytecodeReverts(bytes32,bytes,bytes) (runs: 256, μ: 96880238, ~: 96880072)
+CREATE3Test:testDoubleDeployDifferentBytecodeReverts(bytes32,bytes,bytes) (runs: 256, μ: 96880241, ~: 96880072)
 CREATE3Test:testDoubleDeploySameBytecodeReverts() (gas: 96889159)
-CREATE3Test:testDoubleDeploySameBytecodeReverts(bytes32,bytes) (runs: 256, μ: 96881103, ~: 96881057)
+CREATE3Test:testDoubleDeploySameBytecodeReverts(bytes32,bytes) (runs: 256, μ: 96881101, ~: 96881057)
 CREATE3Test:test__codesize() (gas: 15758)
 DateTimeLibTest:testAddSubDiffDays(uint256,uint256) (runs: 256, μ: 4036, ~: 4074)
 DateTimeLibTest:testAddSubDiffHours(uint256,uint256) (runs: 256, μ: 3978, ~: 3932)
@@ -612,16 +612,16 @@ LibStringTest:testToStringZeroBrutalized() (gas: 597698)
 LibStringTest:testToStringZeroRightPadded(uint256) (runs: 256, μ: 728906, ~: 597374)
 LibStringTest:test__codesize() (gas: 39660)
 LibZipTest:testCdCompress() (gas: 166388)
-LibZipTest:testCdCompressDecompress(bytes) (runs: 256, μ: 791207, ~: 639141)
-LibZipTest:testCdCompressDecompress(uint256) (runs: 256, μ: 789894, ~: 694403)
+LibZipTest:testCdCompressDecompress(bytes) (runs: 256, μ: 797816, ~: 640136)
+LibZipTest:testCdCompressDecompress(uint256) (runs: 256, μ: 790014, ~: 697705)
 LibZipTest:testCdFallback() (gas: 5691887)
-LibZipTest:testCdFallback(bytes,uint256) (runs: 256, μ: 1198096, ~: 1040825)
-LibZipTest:testCdFallbackMaskTrick(uint256) (runs: 256, μ: 638, ~: 611)
-LibZipTest:testDecompressWontRevert(bytes) (runs: 256, μ: 720462, ~: 618115)
-LibZipTest:testFlzCompressDecompress() (gas: 2149416)
-LibZipTest:testFlzCompressDecompress(bytes) (runs: 256, μ: 859748, ~: 675014)
-LibZipTest:testFlzCompressDecompress2() (gas: 1001791)
-LibZipTest:test__codesize() (gas: 20650)
+LibZipTest:testCdFallback(bytes,uint256) (runs: 256, μ: 1212573, ~: 1033427)
+LibZipTest:testCdFallbackMaskTrick(uint256,uint256) (runs: 256, μ: 690, ~: 663)
+LibZipTest:testDecompressWontRevert(bytes) (runs: 256, μ: 734431, ~: 618862)
+LibZipTest:testFlzCompressDecompress() (gas: 2151512)
+LibZipTest:testFlzCompressDecompress(bytes) (runs: 256, μ: 878240, ~: 675310)
+LibZipTest:testFlzCompressDecompress2() (gas: 1003822)
+LibZipTest:test__codesize() (gas: 20689)
 MerkleProofLibTest:testEmptyCalldataHelpers() (gas: 1086)
 MerkleProofLibTest:testVerifyMultiProof(bool,bool,bool,bool,bytes32) (runs: 256, μ: 718173, ~: 630726)
 MerkleProofLibTest:testVerifyMultiProofForHeightOneTree(bool,bool,bool,bool,bool,bool[]) (runs: 256, μ: 33429, ~: 32418)
diff --git a/src/utils/LibZip.sol b/src/utils/LibZip.sol
index 3eb9cc7c4..641d1f752 100644
--- a/src/utils/LibZip.sol
+++ b/src/utils/LibZip.sol
@@ -255,7 +255,7 @@ library LibZip {
         assembly {
             if iszero(calldatasize()) { return(calldatasize(), calldatasize()) }
             let o := 0
-            let f := sub(0, 4) // For negating the first 4 bytes.
+            let f := not(3) // For negating the first 4 bytes.
             for { let i := 0 } lt(i, calldatasize()) {} {
                 let c := byte(0, xor(add(i, f), calldataload(i)))
                 i := add(i, 1)
diff --git a/test/LibZip.t.sol b/test/LibZip.t.sol
index d04dea79f..e9f534e03 100644
--- a/test/LibZip.t.sol
+++ b/test/LibZip.t.sol
@@ -235,18 +235,15 @@ contract LibZipTest is SoladyTest {
         assertTrue(success);
     }
 
-    function testCdFallbackMaskTrick(uint256 i) public {
+    function testCdFallbackMaskTrick(uint256 i, uint256 j) public {
         i = _bound(i, 0, 2 ** 248 - 1);
-        uint256 mask;
+        uint256 a;
+        uint256 b;
         /// @solidity memory-safe-assembly
         assembly {
-            let f := sub(0, 4)
-            mask := byte(0, add(i, f))
-        }
-        if (i < 4) {
-            assertEq(mask, 0xff);
-        } else {
-            assertEq(mask, 0x00);
+            a := byte(0, xor(add(i, not(3)), j))
+            b := xor(byte(i, shl(224, 0xffffffff)), byte(0, j))
         }
+        assertEq(a, b);
     }
 }