diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
index d7c05c0a48e88..3511775de08f1 100644
--- a/sessionctx/variable/tidb_vars.go
+++ b/sessionctx/variable/tidb_vars.go
@@ -1079,7 +1079,7 @@ const (
 	DefTiDBForeignKeyChecks                      = false
 	DefTiDBAnalyzePartitionConcurrency           = 1
 	DefTiDBOptRangeMaxSize                       = 64 * int64(size.MB) // 64 MB
-	DefTiDBCostModelVer                          = 2
+	DefTiDBCostModelVer                          = 1
 	DefTiDBServerMemoryLimitSessMinSize          = 128 << 20
 	DefTiDBMergePartitionStatsConcurrency        = 1
 	DefTiDBServerMemoryLimitGCTrigger            = 0.7