diff --git a/web/includes/functions.php b/web/includes/functions.php
index 30dc9fba5..b8c0a0de0 100644
--- a/web/includes/functions.php
+++ b/web/includes/functions.php
@@ -2139,7 +2139,8 @@ function cache_bust( $file ) {
   # Use the last modified timestamp to create a link that gets a different filename
   # To defeat caching.  Should probably use md5 hash
   $parts = pathinfo($file);
-  $cacheFile = 'cache/'.$parts['filename'].'-'.$_COOKIE['zmCSS'].'-'.filemtime($file).'.'.$parts['extension'];
+  global $css;
+  $cacheFile = 'cache/'.$parts['filename'].'-'.$css.'-'.filemtime($file).'.'.$parts['extension'];
   if ( file_exists( ZM_PATH_WEB.'/'.$cacheFile ) or symlink( ZM_PATH_WEB.'/'.$file, ZM_PATH_WEB.'/'.$cacheFile ) ) {
     return $cacheFile;
   } else {