diff --git a/examples/call/contracts/Universal.sol b/examples/call/contracts/Universal.sol
index 5b9f6c05..df362796 100644
--- a/examples/call/contracts/Universal.sol
+++ b/examples/call/contracts/Universal.sol
@@ -11,10 +11,12 @@ contract Universal is UniversalContract {
 
     event HelloEvent(string, string);
     event RevertEvent(string, RevertContext);
+
     error TransferFailed();
+    error Unauthorized();
 
     modifier onlyGateway() {
-        require(msg.sender == address(gateway), "Caller is not the gateway");
+        if (msg.sender != address(gateway)) revert Unauthorized();
         _;
     }
 
diff --git a/examples/hello/contracts/Universal.sol b/examples/hello/contracts/Universal.sol
index b83fc684..fa4920e9 100644
--- a/examples/hello/contracts/Universal.sol
+++ b/examples/hello/contracts/Universal.sol
@@ -7,9 +7,10 @@ contract Universal is UniversalContract {
     GatewayZEVM public immutable gateway;
 
     event HelloEvent(string, string);
+    error Unauthorized();
 
     modifier onlyGateway() {
-        require(msg.sender == address(gateway), "Caller is not the gateway");
+        if (msg.sender != address(gateway)) revert Unauthorized();
         _;
     }
 
diff --git a/examples/swap/contracts/Swap.sol b/examples/swap/contracts/Swap.sol
index f8c1ebf5..d6c8ade1 100644
--- a/examples/swap/contracts/Swap.sol
+++ b/examples/swap/contracts/Swap.sol
@@ -17,9 +17,10 @@ contract Swap is UniversalContract {
     uint256 constant BITCOIN = 18332;
 
     error InvalidAddress();
+    error Unauthorized();
 
     modifier onlyGateway() {
-        require(msg.sender == address(gateway), "Caller is not the gateway");
+        if (msg.sender != address(gateway)) revert Unauthorized();
         _;
     }
 
diff --git a/examples/swap/contracts/SwapToAnyToken.sol b/examples/swap/contracts/SwapToAnyToken.sol
index 9642687b..d3022c99 100644
--- a/examples/swap/contracts/SwapToAnyToken.sol
+++ b/examples/swap/contracts/SwapToAnyToken.sol
@@ -16,10 +16,12 @@ contract SwapToAnyToken is UniversalContract {
     address public immutable uniswapRouter;
     GatewayZEVM public gateway;
     uint256 constant BITCOIN = 18332;
+
     error InvalidAddress();
+    error Unauthorized();
 
     modifier onlyGateway() {
-        require(msg.sender == address(gateway), "Caller is not the gateway");
+        if (msg.sender != address(gateway)) revert Unauthorized();
         _;
     }