1 files changed, 7 insertions, 3 deletions
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index 6893610e71..40c433d7ae 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -18,6 +18,7 @@ from synapse.api.constants import ThirdPartyEntityKind
 from synapse.api.errors import CodeMessageException
 from synapse.http.client import SimpleHttpClient
 from synapse.events.utils import serialize_event
+from synapse.util.logcontext import preserve_fn, make_deferred_yieldable
 from synapse.util.caches.response_cache import ResponseCache
 from synapse.types import ThirdPartyInstanceID
 
@@ -192,9 +193,12 @@ class ApplicationServiceApi(SimpleHttpClient):
                 defer.returnValue(None)
 
         key = (service.id, protocol)
-        return self.protocol_meta_cache.get(key) or (
-            self.protocol_meta_cache.set(key, _get())
-        )
+        result = self.protocol_meta_cache.get(key)
+        if not result:
+            result = self.protocol_meta_cache.set(
+                key, preserve_fn(_get)()
+            )
+        return make_deferred_yieldable(result)
 
     @defer.inlineCallbacks
     def push_bulk(self, service, events, txn_id=None):