diff --git a/src/content/ftp.js b/src/content/ftp.js
index 1cbf6d2..b7b368a 100644
--- a/src/content/ftp.js
+++ b/src/content/ftp.js
@@ -19,13 +19,13 @@
  */
 
 if (UA.isMozilla) (() => {
-  // see https://dxr.mozilla.org/mozilla-central/rev/d03b538b6b417ba892d0a92fd693945b741246e1/netwerk/streamconv/converters/nsIndexedToHTML.cpp#381
+  // see https://searchfox.org/mozilla-central/rev/76c1ff5f0de23366fe952ab228610ee695a56e68/netwerk/streamconv/converters/nsIndexedToHTML.cpp#334
   'use strict';
   var gTable, gOrderBy, gTBody, gRows, gUI_showHidden;
   document.addEventListener("DOMContentLoaded", function() {
     if ("gUI_showHidden" in window.wrappedJSObject || // scripts are enabled
         !(document.scripts[0] &&
-          /\bgUI_showHidden\b/.test(document.scripts[0].textContent)) // not a FTP dir listing
+          /\bgUI_showHidden\b/.test(document.scripts[0].textContent)) // not a FTP / file:// dir listing
     ) {
       return;
     }
diff --git a/src/content/staticNS.js b/src/content/staticNS.js
index c2da4a3..33278ee 100644
--- a/src/content/staticNS.js
+++ b/src/content/staticNS.js
@@ -152,8 +152,10 @@
           new Set(["script"]), { has() { return true; } });
       } else {
         let perms = policy.permissions;
-        if (!perms.capabilities.includes("script") && /^file:\/\/\/(?:[^#?]+\/)?$/.test(document.URL)) {
-          // allow browser UI scripts for directory navigation
+        if (!(UA.isMozilla || perms.capabilities.includes("script")) &&
+          /^file:\/\/\/(?:[^#?]+\/)?$/.test(document.URL)) {
+          // Allow Chromium browser UI scripts for directory navigation
+          // (for Firefox we rely on emulation in content/ftp.js).
           perms.capabilities.push("script");
         }
         this.capabilities = new Set(perms.capabilities);
diff --git a/src/manifest.json b/src/manifest.json
index 56958a1..19c72c0 100644
--- a/src/manifest.json
+++ b/src/manifest.json
@@ -112,18 +112,12 @@
         "content/content.js"
       ]
     },
-    {
-      "run_at": "document_start",
-      "matches": ["ftp://*/*"],
-      "js": [
-        "content/ftp.js"
-      ]
-    },
     {
       "run_at": "document_start",
       "matches": ["file://*/*", "ftp://*/*"],
       "all_frames": true,
       "js": [
+        "content/ftp.js",
         "lib/DocumentFreezer.js",
         "content/syncFetchPolicy.js"
       ]