diff --git a/dm/syncer/ddl.go b/dm/syncer/ddl.go
index b8304c3b036..02e22cea54b 100644
--- a/dm/syncer/ddl.go
+++ b/dm/syncer/ddl.go
@@ -851,6 +851,9 @@ func (ddl *Optimist) handleDDL(qec *queryEventContext) error {
 			if op.ConflictStage != optimism.ConflictDetected {
 				break
 			}
+			if ddl.strict {
+				return terror.ErrSyncerShardDDLConflict.Generate(qec.needHandleDDLs, op.ConflictMsg)
+			}
 			rev = op.Revision
 			ddl.logger.Info("operation conflict detected, waiting for resolve", zap.Stringer("info", info))
 		}
diff --git a/dm/tests/shardddl4_1/run.sh b/dm/tests/shardddl4_1/run.sh
index b7914bf6fae..8cac95b6ad2 100644
--- a/dm/tests/shardddl4_1/run.sh
+++ b/dm/tests/shardddl4_1/run.sh
@@ -1217,13 +1217,14 @@ function DM_STRICT_OPTIMISTIC_SINGLE_SOURCE_CASE() {
 	run_sql_source1 "insert into ${shardddl1}.${tb1} values(1,1);"
 	run_sql_source1 "insert into ${shardddl1}.${tb2} values(2,2);"
 
-	run_sql_source1 "alter table ${shardddl1}.${tb1} add c int;"
+	run_sql_source1 "alter table ${shardddl1}.${tb1} add c int not null default 10;"
 	run_sql_source1 "insert into ${shardddl1}.${tb1} values(3,3,3);"
 	run_sql_source1 "insert into ${shardddl1}.${tb2} values(4,4);"
 
-	run_sql_source1 "alter table ${shardddl1}.${tb2} change b c int;"
+	run_sql_source1 "alter table ${shardddl1}.${tb2} add c varchar(30) not null default '10';"
 	run_dm_ctl_with_retry $WORK_DIR "127.0.0.1:$MASTER_PORT" \
 		"query-status test" \
+		'"stage": "Paused"' 1 \
 		"because schema conflict detected" 1
 }