diff --git a/src/utils/LibSort.sol b/src/utils/LibSort.sol
index ac2df8336..a5af33f71 100644
--- a/src/utils/LibSort.sol
+++ b/src/utils/LibSort.sol
@@ -597,29 +597,30 @@ library LibSort {
             }
         }
         if (keys.length == uint256(0)) return;
-        uint256[] memory oriKeys = copy(keys);
-        uint256[] memory oriValues = copy(values);
-        insertionSort(keys);
+        (uint256[] memory oriKeys, uint256[] memory oriValues) = (copy(keys), copy(values));
+        insertionSort(keys); // Optimize for bytecode size.
         uniquifySorted(keys);
         /// @solidity memory-safe-assembly
         assembly {
+            let d := sub(values, keys)
+            let w := not(0x1f)
+            let s := add(keys, 0x20)
             mstore(values, mload(keys)) // Truncate.
-            calldatacopy(add(values, 0x20), calldatasize(), shl(5, mload(keys))) // Zeroize.
-            let end := add(0x20, shl(5, mload(oriKeys)))
-            for { let i := 0x20 } 1 {} {
+            calldatacopy(add(s, d), calldatasize(), shl(5, mload(keys))) // Zeroize.
+            for { let i := shl(5, mload(oriKeys)) } 1 {} {
                 let k := mload(add(oriKeys, i))
                 let v := mload(add(oriValues, i))
-                let j := 0x20
-                for {} iszero(eq(mload(add(keys, j)), k)) {} { j := add(j, 0x20) }
-                let s := add(mload(add(values, j)), v)
-                if lt(s, v) {
+                let j := s
+                for {} iszero(eq(mload(j), k)) {} { j := add(j, 0x20) }
+                j := add(j, d)
+                mstore(j, add(mload(j), v))
+                if lt(mload(j), v) {
                     mstore(0x00, 0x4e487b71)
                     mstore(0x20, 0x11) // Overflow panic.
                     revert(0x1c, 0x24)
                 }
-                mstore(add(values, j), s)
-                i := add(i, 0x20)
-                if eq(i, end) { break }
+                i := add(i, w)
+                if iszero(i) { break }
             }
             mstore(0x40, m) // Frees the temporary memory.
         }
diff --git a/test/LibSort.t.sol b/test/LibSort.t.sol
index 5d2370176..3ca410492 100644
--- a/test/LibSort.t.sol
+++ b/test/LibSort.t.sol
@@ -1298,6 +1298,24 @@ contract LibSortTest is SoladyTest {
         assertEq(orAll >> 160, 0);
     }
 
+    function testGroupSum() public {
+        uint256 n = 32;
+        uint256[] memory keys = new uint256[](n);
+        uint256[] memory values = new uint256[](n);
+        uint256 total;
+        unchecked {
+            for (uint256 i; i < n; ++i) {
+                keys[i] = (i + 1) % 7;
+                values[i] = i;
+                total += i;
+            }
+        }
+        LibSort.groupSum(keys, values);
+        assertEq(keys.length, 7);
+        assertEq(values.length, 7);
+        assertEq(_sum(values), total);
+    }
+
     function testGroupSum(bytes32) public {
         if (_randomChance(2)) {
             _misalignFreeMemoryPointer();