diff --git a/util/request_source.go b/util/request_source.go
index 718fd9450..eba974773 100644
--- a/util/request_source.go
+++ b/util/request_source.go
@@ -25,8 +25,6 @@ const (
 	InternalTxnGC = "gc"
 	// InternalTxnMeta is the type of the miscellaneous meta usage.
 	InternalTxnMeta = InternalTxnOthers
-	// InternalTxnDDL is the type of inner DDL sql.
-	InternalTxnDDL = "ddl"
 )
 
 const (