diff --git a/migrator/migrator.go b/migrator/migrator.go
index 95b2d75b..5ab1c126 100644
--- a/migrator/migrator.go
+++ b/migrator/migrator.go
@@ -449,11 +449,13 @@ func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnTy
 	}
 
 	// check default value
-	if v, ok := columnType.DefaultValue(); ok &&
-		utils.CheckColumnDefaultNull(v) != utils.CheckColumnDefaultNull(field.DefaultValue) {
-		// not primary key
-		if !field.PrimaryKey {
-			alterColumn = true
+	if v, ok := columnType.DefaultValue(); ok && v != field.DefaultValue {
+		// not all equal null
+		if !(utils.CheckColumnDefaultNull(v) && utils.CheckColumnDefaultNull(field.DefaultValue)) {
+			// not primary key
+			if !field.PrimaryKey {
+				alterColumn = true
+			}
 		}
 	}
 
diff --git a/tests/migrate_test.go b/tests/migrate_test.go
index 7ef81a35..9da9f3d7 100644
--- a/tests/migrate_test.go
+++ b/tests/migrate_test.go
@@ -687,7 +687,7 @@ func TestUniqueColumn(t *testing.T) {
 	AssertEqual(t, true, DB.Migrator().HasIndex(&UniqueTest{}, "name"))
 	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest{}, "name_1"))
 	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest{}, "name_2"))
-	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest{}, "name_2"))
+	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest{}, "name_3"))
 
 	type UniqueTest2 struct {
 		ID   string `gorm:"primary_key"`
@@ -712,5 +712,5 @@ func TestUniqueColumn(t *testing.T) {
 	AssertEqual(t, true, DB.Migrator().HasIndex(&UniqueTest2{}, "name"))
 	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest2{}, "name_1"))
 	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest2{}, "name_2"))
-	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest2{}, "name_2"))
+	AssertEqual(t, false, DB.Migrator().HasIndex(&UniqueTest2{}, "name_3"))
 }
diff --git a/utils/utils.go b/utils/utils.go
index 78af8d64..95ac4120 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -47,7 +47,7 @@ func CheckTruth(vals ...string) bool {
 }
 
 func CheckColumnDefaultNull(val string) bool {
-	if val == "" || !strings.EqualFold(val, "NULL") {
+	if val == "" || strings.EqualFold(val, "NULL") {
 		return true
 	}
 	return false