diff --git a/ethers-middleware/tests/solidity-contracts/DSProxy.sol b/ethers-middleware/tests/solidity-contracts/DSProxy.sol
index 9bf010f5..267d90cf 100644
--- a/ethers-middleware/tests/solidity-contracts/DSProxy.sol
+++ b/ethers-middleware/tests/solidity-contracts/DSProxy.sol
@@ -48,7 +48,7 @@ contract DSAuth is DSAuthEvents {
             return true;
         } else if (src == owner) {
             return true;
-        } else if (authority == DSAuthority(0)) {
+        } else if (authority == DSAuthority(address(uint160(0)))) {
             return false;
         } else {
             return authority.canCall(src, address(this), sig);