diff --git a/ddl/ddl.go b/ddl/ddl.go
index c9ba3a768a577..28d15245ab3d8 100644
--- a/ddl/ddl.go
+++ b/ddl/ddl.go
@@ -755,6 +755,8 @@ func (d *ddl) Start(ctxPool *pools.ResourcePool) error {
 	d.sessPool = sess.NewSessionPool(ctxPool, d.store)
 	d.ownerManager.SetBeOwnerHook(func() {
 		var err error
+		d.ddlSeqNumMu.Lock()
+		defer d.ddlSeqNumMu.Unlock()
 		d.ddlSeqNumMu.seqNum, err = d.GetNextDDLSeqNum()
 		if err != nil {
 			logutil.BgLogger().Error("error when getting the ddl history count", zap.Error(err))