diff --git a/scripts/synapse_port_db b/scripts/synapse_port_db
index acd9ac4b75..9a0fbc61d8 100755
--- a/scripts/synapse_port_db
+++ b/scripts/synapse_port_db
@@ -196,6 +196,9 @@ class MockHomeserver:
     def get_reactor(self):
         return reactor
 
+    def get_instance_name(self):
+        return "master"
+
 
 class Porter(object):
     def __init__(self, **kwargs):