problem with get_users() meta_query

I am trying to retrieve a list of users that have a value of 'Yes' in one meta field, and a value that is NOT 'Disabled' in another meta field. The code below will find all users with 'Yes' for gtt_comment_optin, and 'Disabled' for gtt_account_status. I have tried changing the compare for gtt_account_status to '!=' as well as 'NOT LIKE' but then I get no result at all.

$args = array(
'meta_query' => array(
	'relation' => 'AND',
		array(
			'key' => 'gtt_comment_optin',
			'value' => 'Yes',
		),
		array(
			'key' => 'gtt_account_status',
			'value' => 'Disabled',
			'compare' => '=',
		),
	),
);

$users = get_users($args);