diff --git a/roomserver/internal/input/input_membership.go b/roomserver/internal/input/input_membership.go
index ff3ed7e5d..3953586b2 100644
--- a/roomserver/internal/input/input_membership.go
+++ b/roomserver/internal/input/input_membership.go
@@ -48,7 +48,7 @@ func (r *Inputer) updateMemberships(
 	// Load the event JSON so we can look up the "membership" key.
 	// TODO: Maybe add a membership key to the events table so we can load that
 	// key without having to load the entire event JSON?
-	events, err := r.DB.Events(ctx, eventNIDs)
+	events, err := updater.Events(ctx, eventNIDs)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/events_table.go b/roomserver/storage/postgres/events_table.go
index ece1d9e3c..c136f039a 100644
--- a/roomserver/storage/postgres/events_table.go
+++ b/roomserver/storage/postgres/events_table.go
@@ -74,7 +74,7 @@ const insertEventSQL = "" +
 	"INSERT INTO roomserver_events AS e (room_nid, event_type_nid, event_state_key_nid, event_id, reference_sha256, auth_event_nids, depth, is_rejected)" +
 	" VALUES ($1, $2, $3, $4, $5, $6, $7, $8)" +
 	" ON CONFLICT ON CONSTRAINT roomserver_event_id_unique DO UPDATE" +
-	" SET is_rejected = $8 WHERE e.is_rejected = FALSE" +
+	" SET is_rejected = $8 WHERE e.event_id = $4 AND e.is_rejected = FALSE" +
 	" RETURNING event_nid, state_snapshot_nid"
 
 const selectEventSQL = "" +
@@ -192,7 +192,8 @@ func (s *eventStatements) InsertEvent(
 ) (types.EventNID, types.StateSnapshotNID, error) {
 	var eventNID int64
 	var stateNID int64
-	err := s.insertEventStmt.QueryRowContext(
+	stmt := sqlutil.TxStmt(txn, s.insertEventStmt)
+	err := stmt.QueryRowContext(
 		ctx, int64(roomNID), int64(eventTypeNID), int64(eventStateKeyNID),
 		eventID, referenceSHA256, eventNIDsAsArray(authEventNIDs), depth,
 		isRejected,
diff --git a/roomserver/storage/shared/membership_updater.go b/roomserver/storage/shared/membership_updater.go
index f1f589a31..66ac2f5b6 100644
--- a/roomserver/storage/shared/membership_updater.go
+++ b/roomserver/storage/shared/membership_updater.go
@@ -136,7 +136,7 @@ func (u *MembershipUpdater) SetToJoin(senderUserID string, eventID string, isUpd
 		}
 
 		// Look up the NID of the new join event
-		nIDs, err := u.d.EventNIDs(u.ctx, []string{eventID})
+		nIDs, err := u.d.eventNIDs(u.ctx, u.txn, []string{eventID})
 		if err != nil {
 			return fmt.Errorf("u.d.EventNIDs: %w", err)
 		}
@@ -170,7 +170,7 @@ func (u *MembershipUpdater) SetToLeave(senderUserID string, eventID string) ([]s
 		}
 
 		// Look up the NID of the new leave event
-		nIDs, err := u.d.EventNIDs(u.ctx, []string{eventID})
+		nIDs, err := u.d.eventNIDs(u.ctx, u.txn, []string{eventID})
 		if err != nil {
 			return fmt.Errorf("u.d.EventNIDs: %w", err)
 		}
@@ -196,7 +196,7 @@ func (u *MembershipUpdater) SetToKnock(event *gomatrixserverlib.Event) (bool, er
 		}
 		if u.membership != tables.MembershipStateKnock {
 			// Look up the NID of the new knock event
-			nIDs, err := u.d.EventNIDs(u.ctx, []string{event.EventID()})
+			nIDs, err := u.d.eventNIDs(u.ctx, u.txn, []string{event.EventID()})
 			if err != nil {
 				return fmt.Errorf("u.d.EventNIDs: %w", err)
 			}