1 files changed, 3 insertions, 0 deletions
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index 9452e7ca9f..c01ba14cd2 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -90,6 +90,9 @@ class SyncRestServlet(RestServlet):
         self._event_serializer = hs.get_event_client_serializer()
 
     async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
+        # This will always be set by the time Twisted calls us.
+        assert request.args is not None
+
         if b"from" in request.args:
             # /events used to use 'from', but /sync uses 'since'.
             # Lets be helpful and whine if we see a 'from'.