diff --git a/synapse/storage/schema/delta/25/guest_access.sql b/synapse/storage/schema/delta/25/guest_access.sql
new file mode 100644

index 0000000000..bdb90e7118
--- /dev/null
+++ b/synapse/storage/schema/delta/25/guest_access.sql
@@ -0,0 +1,25 @@
+/* Copyright 2015 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * This is a manual index of guest_access content of state events,
+ * so that we can join on them in SELECT statements.
+ */
+CREATE TABLE IF NOT EXISTS guest_access(
+    event_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    guest_access TEXT NOT NULL,
+    UNIQUE (event_id)
+);