diff --git a/src/PolygonStateBridge.sol b/src/PolygonStateBridge.sol
index fe43733..a671740 100644
--- a/src/PolygonStateBridge.sol
+++ b/src/PolygonStateBridge.sol
@@ -43,10 +43,12 @@ contract PolygonStateBridge is FxBaseRootTunnel, Ownable2Step {
     /// @notice Emitted when an attempt is made to renounce ownership.
     error CannotRenounceOwnership();
 
-    /// @notice Emitted when an attempt is made to set the FxChildTunnel to the zero address.
+    /// @notice Emitted when an attempt is made to set the FxBaseRootTunnel,
+    /// FxChildTunnel, CheckpointManager or WorldIDIdentityManager addresses to the zero address.
     error AddressZero();
 
-    /// @notice Emitted when an attempt is made to set the FxChildTunnel when it has already been set.
+    /// @notice Emitted when an attempt is made to set the FxBaseRootTunnel's
+    /// fxChildTunnel when it has already been set.
     error FxBaseRootChildTunnelAlreadySet();
 
     ///////////////////////////////////////////////////////////////////
diff --git a/src/PolygonWorldID.sol b/src/PolygonWorldID.sol
index 3c0c779..5cb65ea 100644
--- a/src/PolygonWorldID.sol
+++ b/src/PolygonWorldID.sol
@@ -44,9 +44,14 @@ contract PolygonWorldID is WorldIDBridge, FxBaseChildTunnel, Ownable2Step {
     /// @notice Emitted when an attempt is made to renounce ownership.
     error CannotRenounceOwnership();
 
-    /// @notice Emitted when an attempt is made to set the FxChildTunnel to the zero address.
+    /// @notice Emitted when an attempt is made to set the FxBaseChildTunnel or
+    /// the FxRoot Tunnel to the zero address.
     error AddressZero();
 
+    /// @notice Emitted when an attempt is made to set the FxBaseChildTunnel's 
+    /// fxRootTunnel when it has already been set.
+    error FxBaseChildRootTunnelAlreadySet();
+
     ///////////////////////////////////////////////////////////////////////////////
     ///                                CONSTRUCTION                             ///
     ///////////////////////////////////////////////////////////////////////////////
@@ -127,7 +132,9 @@ contract PolygonWorldID is WorldIDBridge, FxBaseChildTunnel, Ownable2Step {
     ///
     /// @custom:reverts string If the root tunnel has already been set.
     function setFxRootTunnel(address _fxRootTunnel) external virtual override onlyOwner {
-        require(fxRootTunnel == address(0x0), "FxBaseChildTunnel: ROOT_TUNNEL_ALREADY_SET");
+        if (fxRootTunnel != address(0)) {
+            revert FxBaseChildRootTunnelAlreadySet();
+        }
 
         if (_fxRootTunnel == address(0x0)) {
             revert AddressZero();
diff --git a/src/test/PolygonStateBridge.t.sol b/src/test/PolygonStateBridge.t.sol
index b3717c5..698ae15 100644
--- a/src/test/PolygonStateBridge.t.sol
+++ b/src/test/PolygonStateBridge.t.sol
@@ -60,7 +60,8 @@ contract PolygonStateBridgeTest is PRBTest, StdCheats {
     /// @notice Emitted when an attempt is made to set the FxChildTunnel to the zero address.
     error AddressZero();
 
-    /// @notice Emitted when an attempt is made to set the FxChildTunnel when it has already been set.
+    /// @notice Emitted when an attempt is made to set the FxBaseRootTunnel's
+    /// fxChildTunnel when it has already been set.
     error FxBaseRootChildTunnelAlreadySet();
 
     function setUp() public {
@@ -196,7 +197,7 @@ contract PolygonStateBridgeTest is PRBTest, StdCheats {
         polygonStateBridge.setFxChildTunnel(address(0));
     }
 
-    /// @notice tests that the FxChildTunnel can't be set once it has already been set
+    /// @notice tests that the FxBaseRootTunnel's fxChildTunnel can't be set once it has already been set
     function test_cannotSetFxChildTunnelMoreThanOnce_reverts(address _fxChildTunnel) public {
         vm.assume(_fxChildTunnel != address(0));
 
diff --git a/src/test/PolygonWorldID.t.sol b/src/test/PolygonWorldID.t.sol
index 63e8252..01b095d 100644
--- a/src/test/PolygonWorldID.t.sol
+++ b/src/test/PolygonWorldID.t.sol
@@ -33,6 +33,10 @@ contract PolygonWorldIDTest is PRBTest, StdCheats {
     /// @notice Thrown when setFxRootTunnel is called for the first time
     event SetFxRootTunnel(address fxRootTunnel);
 
+    /// @notice Emitted when an attempt is made to set the FxBaseChildTunnel's 
+    /// fxRootTunnel when it has already been set.
+    error FxBaseChildRootTunnelAlreadySet();
+
     function setUp() public {
         /// @notice Initialize the PolygonWorldID contract
         vm.prank(owner);
@@ -108,6 +112,19 @@ contract PolygonWorldIDTest is PRBTest, StdCheats {
         new PolygonWorldID(treeDepth, address(0));
     }
 
+    /// @notice tests that the FxBaseChildTunnel's fxRootTunnel can't be set once it has already been set
+    function test_cannotSetFxRootTunnelMoreThanOnce_reverts(address _fxRootTunnel) public {
+        vm.assume(_fxRootTunnel != address(0));
+
+        vm.prank(owner);
+        id.setFxRootTunnel(_fxRootTunnel);
+
+        vm.expectRevert(FxBaseChildRootTunnelAlreadySet.selector);
+
+        vm.prank(owner);
+        id.setFxRootTunnel(_fxRootTunnel);
+    }
+
     /// @notice Tests that a nonPendingOwner can't accept ownership of PolygonWorldID
     /// @param newOwner the new owner of the contract
     function test_notOwner_acceptOwnership_reverts(address newOwner, address randomAddress)