diff --git a/migrator/migrator.go b/migrator/migrator.go
index c564cb67..c455a294 100644
--- a/migrator/migrator.go
+++ b/migrator/migrator.go
@@ -370,9 +370,9 @@ func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnTy
 			alterColumn = true
 		} else {
 			// has size in data type and not equal
-			matches := regexp.MustCompile(`[^\d](\d+)[^\d]`).FindAllStringSubmatch(realDataType, -1)
-			matches2 := regexp.MustCompile(`[^\d]*(\d+)[^\d]`).FindAllStringSubmatch(fullDataType, -1)
-			if (len(matches) == 1 && matches[0][1] != fmt.Sprint(field.Size)) && (len(matches2) == 1 && matches2[0][1] != fmt.Sprint(length)) {
+			matches := regexp.MustCompile(`[^\d](\d+)[^\d]?`).FindAllStringSubmatch(realDataType, -1)
+			matches2 := regexp.MustCompile(`[^\d]*(\d+)[^\d]?`).FindAllStringSubmatch(fullDataType, -1)
+			if (len(matches) == 1 && matches[0][1] != fmt.Sprint(field.Size) || !field.PrimaryKey) && (len(matches2) == 1 && matches2[0][1] != fmt.Sprint(length)) {
 				alterColumn = true
 			}
 		}
diff --git a/tests/go.mod b/tests/go.mod
index ddb1773b..3fa011f1 100644
--- a/tests/go.mod
+++ b/tests/go.mod
@@ -6,11 +6,11 @@ require (
 	github.com/google/uuid v1.1.1
 	github.com/jinzhu/now v1.1.1
 	github.com/lib/pq v1.6.0
-	gorm.io/driver/mysql v1.0.2
-	gorm.io/driver/postgres v1.0.4
+	gorm.io/driver/mysql v1.0.3
+	gorm.io/driver/postgres v1.0.5
 	gorm.io/driver/sqlite v1.1.3
 	gorm.io/driver/sqlserver v1.0.5
-	gorm.io/gorm v1.20.2
+	gorm.io/gorm v1.20.4
 )
 
 replace gorm.io/gorm => ../
diff --git a/tests/migrate_test.go b/tests/migrate_test.go
index 4cc8a7c3..275fe634 100644
--- a/tests/migrate_test.go
+++ b/tests/migrate_test.go
@@ -48,11 +48,13 @@ func TestMigrate(t *testing.T) {
 }
 
 func TestSmartMigrateColumn(t *testing.T) {
+	fullSupported := map[string]bool{"mysql": true, "postgres": true}[DB.Dialector.Name()]
+
 	type UserMigrateColumn struct {
 		ID       uint
 		Name     string
 		Salary   float64
-		Birthday time.Time
+		Birthday time.Time `gorm:"precision:4"`
 	}
 
 	DB.Migrator().DropTable(&UserMigrateColumn{})
@@ -78,15 +80,15 @@ func TestSmartMigrateColumn(t *testing.T) {
 	for _, columnType := range columnTypes {
 		switch columnType.Name() {
 		case "name":
-			if length, _ := columnType.Length(); length != 0 && length != 128 {
+			if length, _ := columnType.Length(); (fullSupported || length != 0) && length != 128 {
 				t.Fatalf("name's length should be 128, but got %v", length)
 			}
 		case "salary":
-			if precision, o, _ := columnType.DecimalSize(); precision != 0 && precision != 2 {
+			if precision, o, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 2 {
 				t.Fatalf("salary's precision should be 2, but got %v %v", precision, o)
 			}
 		case "birthday":
-			if precision, _, _ := columnType.DecimalSize(); precision != 0 && precision != 2 {
+			if precision, _, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 2 {
 				t.Fatalf("birthday's precision should be 2, but got %v", precision)
 			}
 		}
@@ -111,15 +113,15 @@ func TestSmartMigrateColumn(t *testing.T) {
 	for _, columnType := range columnTypes {
 		switch columnType.Name() {
 		case "name":
-			if length, _ := columnType.Length(); length != 0 && length != 256 {
+			if length, _ := columnType.Length(); (fullSupported || length != 0) && length != 256 {
 				t.Fatalf("name's length should be 128, but got %v", length)
 			}
 		case "salary":
-			if precision, _, _ := columnType.DecimalSize(); precision != 0 && precision != 3 {
+			if precision, _, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 3 {
 				t.Fatalf("salary's precision should be 2, but got %v", precision)
 			}
 		case "birthday":
-			if precision, _, _ := columnType.DecimalSize(); precision != 0 && precision != 3 {
+			if precision, _, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 3 {
 				t.Fatalf("birthday's precision should be 2, but got %v", precision)
 			}
 		}