diff --git a/Gruntfile.js b/Gruntfile.js
index 120ddf5..26286d8 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -13,7 +13,7 @@ function firefox_manifest(src, path) {
         // https://bugzilla.mozilla.org/show_bug.cgi?id=1736575
         for(let s of obj.content_scripts)
             if(s.world==='MAIN') {
-                s.js = []; // will be injected by content_script.js
+                s.js = ['/assets/xhr_hook_injector.js'];
                 delete s.world;
             }
 
diff --git a/pakkujs/assets/xhr_hook_injector.js b/pakkujs/assets/xhr_hook_injector.js
new file mode 100644
index 0000000..288cbe2
--- /dev/null
+++ b/pakkujs/assets/xhr_hook_injector.js
@@ -0,0 +1,6 @@
+// used for firefox
+
+console.log('pakku: inject xhr hook');
+let sc = document.createElement('script');
+sc.src = chrome.runtime.getURL('/assets/xhr_hook.js');
+document.documentElement.appendChild(sc);
\ No newline at end of file
diff --git a/pakkujs/core/main.ts b/pakkujs/core/main.ts
index d6b7ccc..efa6f1f 100644
--- a/pakkujs/core/main.ts
+++ b/pakkujs/core/main.ts
@@ -136,11 +136,4 @@ window.addEventListener('message',async function(event) {
 
         handle_task(url[0], url[1], sendResponse, local_config, tabid as int);
     }
-},false);
-
-if(process.env.PAKKU_CHANNEL === 'firefox') {
-    console.log('pakku: inject xhr hook');
-    let sc = document.createElement('script');
-    sc.src = chrome.runtime.getURL('/assets/xhr_hook.js');
-    document.documentElement.appendChild(sc);
-}
\ No newline at end of file
+},false);
\ No newline at end of file
diff --git a/pakkujs/core/post_combine.ts b/pakkujs/core/post_combine.ts
index b9548b9..3701bc8 100644
--- a/pakkujs/core/post_combine.ts
+++ b/pakkujs/core/post_combine.ts
@@ -239,7 +239,7 @@ export function post_combine(input: DanmuClusterOutput, prev_input: DanmuCluster
             }
         }
 
-        // it seems that hot colorful danmus have style may issues, so we remove the colorful if hot
+        // it seems that hot colorful danmus may have style issues, so we remove the colorful if hot
         if(dm.extra.proto_attr &&  (dm.extra.proto_attr & 4)) {
             dm.extra.proto_colorful = 0;
         }