diff --git a/synapse/server.pyi b/synapse/server.pyi
index 3844f0e12f..9d1dfa71e7 100644
--- a/synapse/server.pyi
+++ b/synapse/server.pyi
@@ -114,3 +114,5 @@ class HomeServer(object):
         pass
     def is_mine_id(self, domain_id: str) -> bool:
         pass
+    def get_instance_id(self) -> str:
+        pass