diff --git a/synapse/storage/schema/delta/23/drop_state_index.sql b/synapse/storage/schema/delta/23/drop_state_index.sql
new file mode 100644
index 0000000000..07d0ea5cb2
--- /dev/null
+++ b/synapse/storage/schema/delta/23/drop_state_index.sql
@@ -0,0 +1,16 @@
+/* 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.
+ */
+
+DROP INDEX IF EXISTS state_groups_state_tuple;