Admin url problem

Hi,

I’m using the paid version of Gtranslate.
I selected the sub directory URL.
When I use admin_url function to get the admin-ajax.php url, WP returns the language prepended url like ‘/en/wp-admin/admin-ajax.php’.

admin_url('admin-ajax.php');

But the language prepended url doesn’t exist.
The request returns 404 not found.

How can I fix this?

Thanks.