diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index b333175349..e8e3173ca2 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -284,6 +284,7 @@ class FederationHandler(BaseHandler):
                     [dest],
                     event_id,
                     outlier=True,
+                    timeout=10000,
                 )
                 for event_id in missing_auth
             ],