diff --git a/themes/seven/template.php b/themes/seven/template.php
index 437e9a7..5c086fa 100644
--- a/themes/seven/template.php
+++ b/themes/seven/template.php
@@ -104,12 +104,15 @@ function seven_css_alter(&$css) {
   // Use Seven's vertical tabs style instead of the default one.
   if (isset($css['misc/vertical-tabs.css'])) {
     $css['misc/vertical-tabs.css']['data'] = drupal_get_path('theme', 'seven') . '/vertical-tabs.css';
+    $css['misc/vertical-tabs.css']['type'] = 'file';
   }
   if (isset($css['misc/vertical-tabs-rtl.css'])) {
     $css['misc/vertical-tabs-rtl.css']['data'] = drupal_get_path('theme', 'seven') . '/vertical-tabs-rtl.css';
+    $css['misc/vertical-tabs-rtl.css']['type'] = 'file';
   }
   // Use Seven's jQuery UI theme style instead of the default one.
   if (isset($css['misc/ui/jquery.ui.theme.css'])) {
     $css['misc/ui/jquery.ui.theme.css']['data'] = drupal_get_path('theme', 'seven') . '/jquery.ui.theme.css';
+    $css['misc/ui/jquery.ui.theme.css']['type'] = 'file';
   }
 }