Check for the 'manage_options' capability instead of the 'administrator'...

... role

Although passing a role in the 'current_user_can' function seems to work, the best practice is to pass a capability, like 'manage_options' in order to check if the user is admin.

Please read the following pages:

* http://codex.wordpress.org/Function_Reference/current_user_can#Notes
* http://core.trac.wordpress.org/ticket/22624