diff --git a/tests/test_aio.py b/tests/test_aio.py
index c1243c1..d88ac18 100644
--- a/tests/test_aio.py
+++ b/tests/test_aio.py
@@ -348,9 +348,13 @@ async def _make_client(warning=None, **kwargs):
         is emitted (if any) and that the patch is properly applied by
         consuming the RuntimeError.
         """
-        with pytest.warns(warning),\
-                pytest.raises(RuntimeError):  # Consume error
-            await make_aio_client(addressbook.AddressBookService, **kwargs)
+        if warning:
+            with pytest.warns(warning),\
+                    pytest.raises(RuntimeError):  # Consume error
+                await make_aio_client(addressbook.AddressBookService, **kwargs)
+        else:
+            with pytest.raises(RuntimeError):  # Consume error
+                await make_aio_client(addressbook.AddressBookService, **kwargs)
 
     def _given_timeout(self):
         """Get the timeout provided to TAsyncSocket."""