diff --git a/dev-helpers/oauth2-redirect.html b/dev-helpers/oauth2-redirect.html
index 87a2eed8f5ef..76908c646fbd 100644
--- a/dev-helpers/oauth2-redirect.html
+++ b/dev-helpers/oauth2-redirect.html
@@ -6,6 +6,14 @@
 <script>
     'use strict';
     function run () {
+        if (!window.opener) {
+            prompt("Run this in devtools on the Swagger UI page to complete auth:", [
+                `swaggerUIRedirectOauth2.auth.code = "${JSON.stringify((new URLSearchParams(location.search)).get('code'))}";`
+                `delete swaggerUIRedirectOauth2.state;`,
+                `swaggerUIRedirectOauth2.callback({ auth: swaggerUIRedirectOauth2.auth, redirectUrl: swaggerUIRedirectOauth2.redirectUrl});`,
+            ].join(" "));
+            return;
+        }
         var oauth2 = window.opener.swaggerUIRedirectOauth2;
         var sentState = oauth2.state;
         var redirectUrl = oauth2.redirectUrl;