diff --git a/ext/src/main.js b/ext/src/main.js
index c0293bd..f573bf9 100755
--- a/ext/src/main.js
+++ b/ext/src/main.js
@@ -91,6 +91,12 @@ async function createMenus () {
       , id: "contextCast"
       , title: _("contextCast")
       , visible: options.mirroringEnabled
+
+        // Mirroring doesn't work from local files
+      , documentUrlPatterns: [
+            "http://*/*"
+          , "https://*/*"
+        ]
     });
 }