diff --git a/src/mocks/PendingBlkTimeAndNrAdvanceCheck.sol b/src/mocks/PendingBlkTimeAndNrAdvanceCheck.sol
index 22b6868c..0676845a 100644
--- a/src/mocks/PendingBlkTimeAndNrAdvanceCheck.sol
+++ b/src/mocks/PendingBlkTimeAndNrAdvanceCheck.sol
@@ -9,21 +9,20 @@ import "../precompiles/ArbSys.sol";
 contract PendingBlkTimeAndNrAdvanceCheck {
     uint256 immutable deployedAt;
     uint256 immutable deployedAtBlock;
+    ArbSys constant ARB_SYS = ArbSys(address(100));
 
     constructor() {
         deployedAt = block.timestamp;
-        deployedAtBlock = ArbSys(address(100)).arbBlockNumber();
+        deployedAtBlock = ARB_SYS.arbBlockNumber();
     }
 
     function isAdvancing() external {
         require(block.timestamp > deployedAt, "Time didn't advance");
-        require(ArbSys(address(100)).arbBlockNumber() > deployedAtBlock, "Block didn't advance");
+        require(ARB_SYS.arbBlockNumber() > deployedAtBlock, "Block didn't advance");
     }
 
     function checkArbBlockHashReturnsLatest(bytes32 expected) external {
-        bytes32 gotBlockHash = ArbSys(address(100)).arbBlockHash(
-            ArbSys(address(100)).arbBlockNumber() - 1
-        );
+        bytes32 gotBlockHash = ARB_SYS.arbBlockHash(ARB_SYS.arbBlockNumber() - 1);
         require(gotBlockHash != bytes32(0), "ZERO_BLOCK_HASH");
         require(gotBlockHash == expected, "WRONG_BLOCK_HASH");
     }