diff --git a/parser/parser_test.go b/parser/parser_test.go
index 98f90a0104a5c..dae08a80afde3 100644
--- a/parser/parser_test.go
+++ b/parser/parser_test.go
@@ -3244,6 +3244,7 @@ func TestDDL(t *testing.T) {
 		{"create table t (a bigint, b bigint as (a+1) not null);", true, "CREATE TABLE `t` (`a` BIGINT,`b` BIGINT GENERATED ALWAYS AS(`a`+1) VIRTUAL NOT NULL)"},
 		{"create table t (a bigint, b bigint as (a+1) not null);", true, "CREATE TABLE `t` (`a` BIGINT,`b` BIGINT GENERATED ALWAYS AS(`a`+1) VIRTUAL NOT NULL)"},
 		{"create table t (a bigint, b bigint as (a+1) not null comment 'ttt');", true, "CREATE TABLE `t` (`a` BIGINT,`b` BIGINT GENERATED ALWAYS AS(`a`+1) VIRTUAL NOT NULL COMMENT 'ttt')"},
+		{"create table t(a int, index idx((cast(a as binary(1)))));", true, "CREATE TABLE `t` (`a` INT,INDEX `idx`((CAST(`a` AS BINARY(1)))))"},
 		{"alter table t add column (f timestamp as (a+1) default '2019-01-01 11:11:11');", false, ""},
 		{"alter table t modify column f int as (a+1) default 55;", false, ""},
 
diff --git a/parser/types/field_type.go b/parser/types/field_type.go
index ff0ac9793cf17..991dc3d087d75 100644
--- a/parser/types/field_type.go
+++ b/parser/types/field_type.go
@@ -518,7 +518,7 @@ func (ft *FieldType) Restore(ctx *format.RestoreCtx) error {
 // RestoreAsCastType is used for write AST back to string.
 func (ft *FieldType) RestoreAsCastType(ctx *format.RestoreCtx, explicitCharset bool) {
 	switch ft.tp {
-	case mysql.TypeVarString:
+	case mysql.TypeVarString, mysql.TypeString:
 		skipWriteBinary := false
 		if ft.charset == charset.CharsetBin && ft.collate == charset.CollationBin {
 			ctx.WriteKeyWord("BINARY")