changing label_user no longer works

trying to change label_username, via general_template.php in wp-include.

line 405

changing to

‘label_username’ => __( ‘Email /Username’ ),

has no effect also tried adding tis to functions again with no effect, cache is cleared. 3.9.1

function wpse60605_change_username_label( $defaults ){
$defaults[‘label_username’] = __( ‘Username or Email’ );
return $defaults;
}
add_filter( ‘login_form_defaults’, ‘wpse60605_change_username_label’ );