diff --git a/migrator.go b/migrator.go
index 0e01f567..3d2b032b 100644
--- a/migrator.go
+++ b/migrator.go
@@ -87,6 +87,8 @@ type Migrator interface {
 	DropColumn(dst interface{}, field string) error
 	AlterColumn(dst interface{}, field string) error
 	MigrateColumn(dst interface{}, field *schema.Field, columnType ColumnType) error
+	// MigrateColumnUnique migrate column's UNIQUE constraint, it's part of MigrateColumn.
+	MigrateColumnUnique(dst interface{}, field *schema.Field, columnType ColumnType) error
 	HasColumn(dst interface{}, field string) bool
 	RenameColumn(dst interface{}, oldName, field string) error
 	ColumnTypes(dst interface{}) ([]ColumnType, error)