diff --git a/src/js/messaging.js b/src/js/messaging.js
index 0cc176849..74e761963 100644
--- a/src/js/messaging.js
+++ b/src/js/messaging.js
@@ -1858,13 +1858,13 @@ const onMessage = function(request, sender, callback) {
         break;
 
     case 'subscribeTo':
+        // https://github.com/uBlockOrigin/uBlock-issues/issues/1797
+        if ( /^(file|https?):\/\//.test(request.location) === false ) { break; }
         const url = encodeURIComponent(request.location);
         const title = encodeURIComponent(request.title);
         const hash = µb.selectedFilterLists.indexOf(request.location) !== -1
             ? '#subscribed'
             : '';
-        // https://github.com/uBlockOrigin/uBlock-issues/issues/1797
-        if ( /^(file|https?):\/\//.test(url) === false ) { break; }
         vAPI.tabs.open({
             url: `/asset-viewer.html?url=${url}&title=${title}&subscribe=1${hash}`,
             select: true,