diff --git a/helper/schema/set.go b/helper/schema/set.go
index 92966ea59..689be4f9f 100644
--- a/helper/schema/set.go
+++ b/helper/schema/set.go
@@ -1,6 +1,7 @@
 package schema
 
 import (
+	"fmt"
 	"sort"
 	"sync"
 )
@@ -100,6 +101,10 @@ func (s *Set) Union(other *Set) *Set {
 	return result
 }
 
+func (s *Set) GoString() string {
+	return fmt.Sprintf("*Set(%#v)", s.m)
+}
+
 func (s *Set) init() {
 	s.m = make(map[int]interface{})
 }