diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 4946afe635..275fef1f66 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -53,6 +53,7 @@ ProfileInfo = namedtuple("ProfileInfo", ("avatar_url", "display_name"))
 MemberSummary = namedtuple("MemberSummary", ("members", "count"))
 
 _MEMBERSHIP_PROFILE_UPDATE_NAME = "room_membership_profile_update"
+_CURRENT_STATE_MEMBERSHIP_UPDATE_NAME = "current_state_events_membership"
 
 
 class RoomMemberWorkerStore(EventsWorkerStore):
@@ -602,6 +603,10 @@ class RoomMemberStore(RoomMemberWorkerStore):
         self.register_background_update_handler(
             _MEMBERSHIP_PROFILE_UPDATE_NAME, self._background_add_membership_profile
         )
+        self.register_background_update_handler(
+            _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME,
+            self._background_current_state_membership,
+        )
 
     def _store_room_members_txn(self, txn, events, backfilled):
         """Store a room member in the database.
@@ -781,6 +786,52 @@ class RoomMemberStore(RoomMemberWorkerStore):
 
         defer.returnValue(result)
 
+    @defer.inlineCallbacks
+    def _background_current_state_membership(self, progress, batch_size):
+        """Update the new membership column on current_state_events.
+        """
+
+        if "rooms" not in progress:
+            rooms = yield self._simple_select_onecol(
+                table="current_state_events",
+                keyvalues={},
+                retcol="DISTINCT room_id",
+                desc="_background_current_state_membership_get_rooms",
+            )
+            progress["rooms"] = rooms
+
+        rooms = progress["rooms"]
+
+        def _background_current_state_membership_txn(txn):
+            processed = 0
+            while rooms and processed < batch_size:
+                sql = """
+                    UPDATE current_state_events AS c
+                    SET membership = (
+                        SELECT membership FROM room_memberships
+                        WHERE event_id = c.event_id
+                    )
+                    WHERE room_id = ?
+                """
+                txn.execute(sql, (rooms.pop(),))
+                processed += txn.rowcount
+
+            self._background_update_progress_txn(
+                txn, _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME, progress
+            )
+
+            return processed
+
+        result = yield self.runInteraction(
+            "_background_current_state_membership_update",
+            _background_current_state_membership_txn,
+        )
+
+        if not rooms:
+            yield self._end_background_update(_CURRENT_STATE_MEMBERSHIP_UPDATE_NAME)
+
+        defer.returnValue(result)
+
 
 class _JoinedHostsCache(object):
     """Cache for joined hosts in a room that is optimised to handle updates
diff --git a/synapse/storage/schema/delta/56/current_state_events_membership.sql b/synapse/storage/schema/delta/56/current_state_events_membership.sql
index 5c754651cb..ec7ad5bae2 100644
--- a/synapse/storage/schema/delta/56/current_state_events_membership.sql
+++ b/synapse/storage/schema/delta/56/current_state_events_membership.sql
@@ -17,3 +17,6 @@
 -- room_memberships, which can be surprisingly costly (we do such queries
 -- very frequently).
 ALTER TABLE current_state_events ADD membership TEXT;
+
+INSERT INTO background_updates (update_name, progress_json) VALUES
+  ('current_state_events_membership', '{}');