diff --git a/synapse/server_notices/resource_limits_server_notices.py b/synapse/server_notices/resource_limits_server_notices.py
index c62a9301f3..e484282529 100644
--- a/synapse/server_notices/resource_limits_server_notices.py
+++ b/synapse/server_notices/resource_limits_server_notices.py
@@ -127,7 +127,7 @@ class ResourceLimitsServerNotices(object):
 
         Args:
             user_id (str): user to notify
-            ref_events ([]): The list of pinned events that are unrelated to
+            ref_events (list[str]): The event_ids of pinned events that are unrelated to
             limit blocking and need to be preserved.
         """
         content = {"pinned": ref_events}