diff --git a/contracts/contracts/opl/Enclave.sol b/contracts/contracts/opl/Enclave.sol
index 30235a45..c6913ff7 100644
--- a/contracts/contracts/opl/Enclave.sol
+++ b/contracts/contracts/opl/Enclave.sol
@@ -1,37 +1,14 @@
 // SPDX-License-Identifier: Apache-2.0
 pragma solidity ^0.8.0;
 
-import {ERC2771Context} from "@openzeppelin/contracts/metatx/ERC2771Context.sol";
-import {Context} from "@openzeppelin/contracts/utils/Context.sol";
-
 import {Endpoint} from "./Endpoint.sol";
 
 /**
  * @title OPL Enclave
  * @dev The Sapphire-side of an OPL dapp.
  */
-contract Enclave is Endpoint, ERC2771Context {
+contract Enclave is Endpoint {
     constructor(address _host, bytes32 _hostChain)
         Endpoint(_host, _hostChain)
-        ERC2771Context(block.chainid == 0x5aff ? address(0) : address(0)) // TODO: insert gsn deployment
     {} // solhint-disable-line no-empty-blocks
-
-    // The following functions are overrides required by Solidity.
-    function _msgData()
-        internal
-        view
-        override(Context, ERC2771Context)
-        returns (bytes calldata)
-    {
-        return ERC2771Context._msgData();
-    }
-
-    function _msgSender()
-        internal
-        view
-        override(Context, ERC2771Context)
-        returns (address)
-    {
-        return ERC2771Context._msgSender();
-    }
 }
diff --git a/contracts/contracts/opl/Endpoint.sol b/contracts/contracts/opl/Endpoint.sol
index dad51aeb..3232af77 100644
--- a/contracts/contracts/opl/Endpoint.sol
+++ b/contracts/contracts/opl/Endpoint.sol
@@ -5,12 +5,6 @@ import {Context} from "@openzeppelin/contracts/utils/Context.sol";
 
 /// Unable to automatically configure OPL. Please use the manual version of the base contract.
 error AutoConfigUnavailable();
-/// The method can only be called by the message bus;
-error NotMessageBus();
-/// Messages may only be sent by the remote endpoint (Enclave or Host).
-error NotRemoteEndpoint();
-/// This message arrived too early or late.
-error WrongSeqNum(uint256 expected, uint256 got);
 /// The remote endpoint's contract address was missing.
 error MissingRemoteAddr();
 /// The remote endpoint's chain ID was missing.
@@ -19,8 +13,6 @@ error MissingRemoteChainId();
 error SelfCallDisallowed();
 /// The requested endpoint does not exist.
 error UnknownEndpoint();
-/// Receiving endpoint did not return successfully.
-error ReceiverError();
 
 /// The outcome of the message call.
 enum Result {
@@ -105,7 +97,8 @@ contract BaseEndpoint is Context {
                 envelope,
                 address(this) // executor
             );
-            if (celerStatus != 1) revert ReceiverError();
+            // Receiving endpoint did not return successfully.
+            require(celerStatus == 1, "ReceiverError");
             if (fee > 0) payable(0).transfer(fee); // burn the fee, for fidelity
         } else {
             ICelerMessageBus(messageBus).sendMessage{value: fee}(
@@ -125,14 +118,19 @@ contract BaseEndpoint is Context {
         bytes calldata _message,
         address // executor
     ) external payable returns (uint256) {
-        if (msg.sender != messageBus) revert NotMessageBus();
-        if (_sender != remote || _senderChainId != remoteChainId)
-            revert NotRemoteEndpoint();
+        // The method can only be called by the message bus;
+        require(_msgSender() == messageBus, "NotMessageBus");
+        // Messages may only be sent by the remote endpoint (Enclave or Host).
+        require(
+            _sender == remote && _senderChainId == remoteChainId,
+            "NotRemoteEndpoint"
+        );
         bytes4 epSel = bytes4(_message[:4]);
         uint256 seq = uint256(bytes32(_message[4:36]));
         bytes calldata message = _message[36:];
         if (inOrder) {
-            if (seq != rxSeq) revert WrongSeqNum(rxSeq, seq);
+            // This message arrived too early or late.
+            require(seq == rxSeq, "WrongSeqNum");
             ++rxSeq;
         }
         function(bytes calldata) returns (Result) ep = endpoints[epSel];