diff --git a/src/etc/inc/authgui.inc b/src/etc/inc/authgui.inc
index 93f54fca9..0e1f488ed 100644
--- a/src/etc/inc/authgui.inc
+++ b/src/etc/inc/authgui.inc
@@ -244,8 +244,8 @@ function display_error_form($http_code, $desc)
 
     <title><?=$http_code?></title>
 
-    <link href="/ui/themes/<?= $themename ?>/build/css/main.css" rel="stylesheet">
-    <link href="/ui/themes/<?= $themename ?>/build/images/favicon.png" rel="shortcut icon">
+    <link href="<?= cache_safe("/ui/themes/{$themename}/build/css/main.css") ?>" rel="stylesheet">
+    <link href="<?= cache_safe("/ui/themes/{$themename}/build/images/favicon.png") ?>" rel="shortcut icon">
 
     <!--[if lt IE 9]><script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.2/html5shiv.min.js"></script><![endif]-->
   </head>
@@ -312,17 +312,15 @@ function display_login_form($Login_Error)
 
     <title><?=gettext("Login"); ?></title>
 
-    <link href="/ui/themes/<?= $themename ?>/build/css/main.css" rel="stylesheet">
-    <link href="/ui/themes/<?= $themename ?>/build/images/favicon.png" rel="shortcut icon">
+    <link href="<?= cache_safe("/ui/themes/{$themename}/build/css/main.css") ?>" rel="stylesheet">
+    <link href="<?= cache_safe("/ui/themes/{$themename}/build/images/favicon.png") ?>" rel="shortcut icon">
 
     <script src="/ui/js/jquery-3.2.1.min.js"></script>
     <script src="/ui/js/jquery-migrate-3.0.1.min.js"></script>
 
-<?php
-    if (file_exists("/usr/local/opnsense/www/themes/".$themename."/build/js/theme.js")):?>
-    <script src="/ui/themes/<?=$themename?>/build/js/theme.js"></script>
-<?php
-    endif;?>
+<?php if (file_exists("/usr/local/opnsense/www/themes/{$themename}/build/js/theme.js")): ?>
+    <script src="<?= cache_safe("/ui/themes/{$themename}/build/js/theme.js") ?>"></script>
+<?php endif ?>
 
     <!--[if lt IE 9]><script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.2/html5shiv.min.js"></script><![endif]-->
 
diff --git a/src/etc/inc/util.inc b/src/etc/inc/util.inc
index 04b2dccb5..9c7c051a8 100644
--- a/src/etc/inc/util.inc
+++ b/src/etc/inc/util.inc
@@ -906,6 +906,15 @@ function url_safe($format, $args = array())
     return vsprintf($format, $args);
 }
 
+function cache_safe($url)
+{
+    $info = stat('/usr/local/opnsense/www/index.php');
+    if (!empty($info['mtime'])) {
+        return "{$url}?v=" . substr(md5($info['mtime']), 0, 16);
+    }
+
+    return $url;
+}
 
 /****f* util/exec_command
  * NAME
diff --git a/src/www/guiconfig.inc b/src/www/guiconfig.inc
index 1c3f66dd9..0a107dc13 100644
--- a/src/www/guiconfig.inc
+++ b/src/www/guiconfig.inc
@@ -61,16 +61,6 @@ function html_safe($text)
     return htmlspecialchars($text, ENT_QUOTES | ENT_HTML401);
 }
 
-function cache_safe($url)
-{
-    $info = stat('/usr/local/opnsense/www/index.php');
-    if (!empty($info['mtime'])) {
-        return "{$url}?v=" . substr(md5($info['mtime']), 0, 16);
-    }
-
-    return $url;
-}
-
 /**
  * search for a themed filename or return distribution standard
  * @param string $url relative url