Theme function showing on wp-login page

Further to livechat:

I am trying to show a news ticker on the frontend of this website. I have the following code in the nsmt child theme's function.php file:

if(!is_admin()) {
if (function_exists (ptmsshow)) ptmsshow();
add_action ('__after_header', 'ptmsshow', 10);

This correctly loads the ticker and places it after the header, and also stops it showing on the admin dashboard.

The issue that I have is that it is still showing on the wp-login.php page. How can I stop this?