diff --git a/ddl/db_integration_test.go b/ddl/db_integration_test.go
index 79cfa4067d953..4a8b7a8a20328 100644
--- a/ddl/db_integration_test.go
+++ b/ddl/db_integration_test.go
@@ -2200,6 +2200,8 @@ func (s *testIntegrationSuite7) TestCreateExpressionIndexError(c *C) {
 	tk.MustExec("drop table if exists t;")
 	tk.MustGetErrCode("create table t (j json, key k (((j,j))))", errno.ErrFunctionalIndexRowValueIsNotAllowed)
 	tk.MustExec("create table t (j json, key k ((j+1),(j+1)))")
+
+	tk.MustGetErrCode("create table t1 (col1 int, index ((concat(''))));", errno.ErrWrongKeyColumnFunctionalIndex)
 }
 
 func (s *testIntegrationSuite7) TestAddExpressionIndexOnPartition(c *C) {
diff --git a/ddl/error.go b/ddl/error.go
index 77e1e19a32c9e..c75ccb1b6d487 100644
--- a/ddl/error.go
+++ b/ddl/error.go
@@ -64,6 +64,8 @@ var (
 	errOnlyOnRangeListPartition = terror.ClassDDL.New(mysql.ErrOnlyOnRangeListPartition, mysql.MySQLErrName[mysql.ErrOnlyOnRangeListPartition])
 	// errWrongKeyColumn is for table column cannot be indexed.
 	errWrongKeyColumn = terror.ClassDDL.New(mysql.ErrWrongKeyColumn, mysql.MySQLErrName[mysql.ErrWrongKeyColumn])
+	// errWrongKeyColumnFunctionalIndex is for expression cannot be indexed.
+	errWrongKeyColumnFunctionalIndex = terror.ClassDDL.New(mysql.ErrWrongKeyColumnFunctionalIndex, mysql.MySQLErrName[mysql.ErrWrongKeyColumnFunctionalIndex])
 	// errWrongFKOptionForGeneratedColumn is for wrong foreign key reference option on generated columns.
 	errWrongFKOptionForGeneratedColumn = terror.ClassDDL.New(mysql.ErrWrongFKOptionForGeneratedColumn, mysql.MySQLErrName[mysql.ErrWrongFKOptionForGeneratedColumn])
 	// ErrUnsupportedOnGeneratedColumn is for unsupported actions on generated columns.
diff --git a/ddl/index.go b/ddl/index.go
index c94f90e53c679..7dfb922045896 100644
--- a/ddl/index.go
+++ b/ddl/index.go
@@ -130,6 +130,9 @@ func checkIndexPrefixLength(columns []*model.ColumnInfo, idxColumns []*model.Ind
 
 func checkIndexColumn(col *model.ColumnInfo, ic *ast.IndexPartSpecification) error {
 	if col.Flen == 0 && (types.IsTypeChar(col.FieldType.Tp) || types.IsTypeVarchar(col.FieldType.Tp)) {
+		if col.GeneratedExprString != "" {
+			return errors.Trace(errWrongKeyColumnFunctionalIndex.GenWithStackByArgs(col.GeneratedExprString))
+		}
 		return errors.Trace(errWrongKeyColumn.GenWithStackByArgs(ic.Column.Name))
 	}