diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index d799e371..dc538b02 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -220,6 +220,7 @@ class Popup {
             this._observeFullscreen(true);
             this._onFullscreenChanged();
             try {
+                Popup._injectStylesheet('yomichan-popup-outer-stylesheet', 'file', '/fg/css/client.css', true);
                 this.setCustomOuterCss(this._options.general.customPopupOuterCss, true);
             } catch (e) {
                 // NOP
diff --git a/ext/manifest.json b/ext/manifest.json
index 68a8adb4..b86459f9 100644
--- a/ext/manifest.json
+++ b/ext/manifest.json
@@ -30,7 +30,6 @@
             "fg/js/frontend.js",
             "fg/js/frontend-initialize.js"
         ],
-        "css": ["fg/css/client.css"],
         "match_about_blank": true,
         "all_frames": true
     }],