diff --git a/contracts/VulnerableBank.sol b/contracts/VulnerableBank.sol
--- a/contracts/VulnerableBank.sol
+++ b/contracts/VulnerableBank.sol
@@
-    function withdraw() public {
-        uint256 amount = balances[msg.sender];
-        (bool success, ) = msg.sender.call{value: amount}("");
-        require(success, "Transfer failed");
-        balances[msg.sender] = 0;
-    }
+    function withdraw() public {
+        uint256 amount = balances[msg.sender];
+        require(amount > 0, "No balance");
+        balances[msg.sender] = 0;
+        (bool success, ) = msg.sender.call{value: amount}("");
+        require(success, "Transfer failed");
+    }