diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index d6643473d..fef87834c 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -310,6 +310,10 @@ class StateStore(SQLBaseStore):
 
         results = {group: {} for group in groups}
         if isinstance(self.database_engine, PostgresEngine):
+            # Temporarily disable sequential scans in this transaction. This is
+            # a temporary hack until we can add the right indices in
+            txn.execute("SET LOCAL enable_seqscan=off")
+
             # The below query walks the state_group tree so that the "state"
             # table includes all state_groups in the tree. It then joins
             # against `state_groups_state` to fetch the latest state.