diff --git a/_includes/comments/giscus.html b/_includes/comments/giscus.html
index 805847202..2d5f7e7bf 100644
--- a/_includes/comments/giscus.html
+++ b/_includes/comments/giscus.html
@@ -39,16 +39,25 @@
     addEventListener('message', (event) => {
       if (event.source === window && event.data && event.data.id === Theme.ID) {
         const newTheme = themeMapper[Theme.visualState];
-
         const message = {
           setConfig: {
             theme: newTheme
           }
         };
 
-        const giscus =
-          document.getElementsByClassName('giscus-frame')[0].contentWindow;
-        giscus.postMessage({ giscus: message }, 'https://giscus.app');
+        const iframe = document.querySelector('.giscus-frame');
+
+        if (!iframe) {
+          return;
+        }
+
+        if (iframe.classList.contains('giscus-frame--loading')) {
+          let url = new URL(iframe.src);
+          url.searchParams.set('theme', newTheme);
+          iframe.src = url.toString();
+        }
+
+        iframe.contentWindow.postMessage({ giscus: message }, 'https://giscus.app');
       }
     });
   })();