diff --git a/synapse/push/baserules.py b/synapse/push/baserules.py
index 286374d0b537..796fa297510b 100644
--- a/synapse/push/baserules.py
+++ b/synapse/push/baserules.py
@@ -335,6 +335,11 @@ def make_base_prepend_rules(kind, modified_base_rules):
                 "_id": "_message",
             }
         ],
+        # default to not notifying for group chats
+        # see https://github.com/vector-im/riot-web/issues/3268
+        # we can't do this on existing servers because we need to
+        # add per-user overrides to preserve their existing behaviour
+        "enabled": False,
         "actions": ["notify", {"set_tweak": "highlight", "value": False}],
     },
     # XXX: this is going to fire for events which aren't m.room.messages