@ -547,7 +547,7 @@ class BaseQuery extends \yii\base\Component
* @param BaseQuery $query the new query to be merged with this query.
* @return BaseQuery the query object itself
*/
public function mergeWith($query)
public function mergeWith(BaseQuery $query)
{
if ($this->select !== $query->select) {
if (empty($this->select)) {