diff --git a/background/usercss-helper.js b/background/usercss-helper.js
index acdb663b..5dd09d59 100644
--- a/background/usercss-helper.js
+++ b/background/usercss-helper.js
@@ -98,7 +98,7 @@ var usercssHelper = (function () {
 
   function openInstallPage(tabId, request) {
     // FIXME: openURL doesn't reuse old page?
-    const url = '/install-usercss/install-usercss.html' +
+    const url = '/install-usercss.html' +
       '?updateUrl=' + encodeURIComponent(request.updateUrl) +
       '&tabId=' + tabId;
     const pending = openURL({url})
diff --git a/install-usercss/install-usercss.html b/install-usercss.html
similarity index 96%
rename from install-usercss/install-usercss.html
rename to install-usercss.html
index 65cdf144..b04f9be0 100644
--- a/install-usercss/install-usercss.html
+++ b/install-usercss.html
@@ -5,7 +5,7 @@
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <meta http-equiv="X-UA-Compatible" content="ie=edge">
   <title>Loading...</title>
-  <link rel="stylesheet" href="install-usercss.css">
+  <link rel="stylesheet" href="/install-usercss/install-usercss.css">
   <script src="/js/messaging.js"></script>
   <script src="/js/prefs.js"></script>
   <script src="/js/dom.js"></script>
@@ -79,6 +79,6 @@
       </div>
     </div>
   </div>
-  <script src="install-usercss.js"></script>
+  <script src="/install-usercss/install-usercss.js"></script>
 </body>
 </html>
\ No newline at end of file