diff --git a/app/main.py b/app/main.py
index 38b5baa..ecbdbb5 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1688,7 +1688,7 @@ def session_view_page(session_id: str, request: Request, user: User = Depends(re
           if (data.ready) {{
             try {{
               const probe = await fetch(iframeSrc, {{method:'HEAD', credentials:'include'}});
-              if (probe.status < 500) {{
+              if (probe.status >= 200 && probe.status < 300) {{
                 const f = document.getElementById('app-frame');
                 f.src = iframeSrc;
                 f.style.display = '';