diff --git a/src/rollup/RollupCore.sol b/src/rollup/RollupCore.sol
index 8378319d..f3cbbc07 100644
--- a/src/rollup/RollupCore.sol
+++ b/src/rollup/RollupCore.sol
@@ -49,6 +49,9 @@ abstract contract RollupCore is IRollupCore, PausableUpgradeable {
     address public stakeToken;
     uint256 public minimumAssertionPeriod;
 
+    // uninitialized
+    uint x;
+
 
     // adding some lines
     mapping(address => bool) public isValidator;