Index: wp-admin/includes/user.php
===================================================================
--- wp-admin/includes/user.php	(revision 13810)
+++ wp-admin/includes/user.php	(working copy)
@@ -685,7 +685,7 @@
 
 		if ( $this->role ) {
 			$this->query_from .= " INNER JOIN $wpdb->usermeta ON $wpdb->users.ID = $wpdb->usermeta.user_id";
-			$this->query_where .= $wpdb->prepare(" AND $wpdb->usermeta.meta_key = '{$wpdb->prefix}capabilities' AND $wpdb->usermeta.meta_value LIKE %s", '%' . $this->role . '%');
+			$this->query_where .= $wpdb->prepare(" AND $wpdb->usermeta.meta_key = '{$wpdb->prefix}capabilities' AND $wpdb->usermeta.meta_value LIKE %s", '%"' . $this->role . '"%');
 		} elseif ( is_multisite() ) {
 			$level_key = $wpdb->get_blog_prefix() . 'capabilities'; // wpmu site admins don't have user_levels
 			$this->query_from .= ", $wpdb->usermeta";