diff --git a/malcolm/core/servercomms.py b/malcolm/core/servercomms.py
index f9fdb8449..1c1eefc16 100644
--- a/malcolm/core/servercomms.py
+++ b/malcolm/core/servercomms.py
@@ -26,7 +26,7 @@ def send_loop(self):
                 self.log_exception(
                     "Exception sending response %s", response.to_dict())
 
-    def send_to_client(response):
+    def send_to_client(self, response):
         """Abstract method to dispatch response to a client
 
         Args:
diff --git a/tests/test_core/test_servercomms.py b/tests/test_core/test_servercomms.py
index a9dd880f8..59a344384 100644
--- a/tests/test_core/test_servercomms.py
+++ b/tests/test_core/test_servercomms.py
@@ -23,7 +23,7 @@ def test_init(self):
 
     def test_not_implemented_error(self):
         server = ServerComms("server", self.process)
-        self.assertRaises(NotImplementedError, server.send_to_client)
+        self.assertRaises(NotImplementedError, server.send_to_client, Mock())
         self.assertRaises(NotImplementedError, server.start_recv_loop)
         self.assertRaises(NotImplementedError, server.stop_recv_loop)