--- a/browser/base/content/test/referrer/head.js
+++ b/browser/base/content/test/referrer/head.js
@@ -204,16 +204,17 @@ function referrerTestCaseLoaded(aTestNum
                              REFERRER_POLICYSERVER_URL_ATTRIBUTE;
   let url = test.fromScheme + server +
             "?scheme=" + escape(test.toScheme) +
             "&policy=" + escape(test.policy || "") +
             "&rel=" + escape(test.rel || "");
   let browser = gTestWindow.gBrowser;
   return BrowserTestUtils.openNewForegroundTab(browser, () => {
     browser.selectedTab = browser.addTab(url, aParams);
+    return url;
   });
 }
 
 /**
  * Checks the result of the referrer test, and moves on to the next test.
  * @param aTestNumber The test number - 0, 1, 2, ...
  * @param aNewWindow The new window where the referrer target opened, or null.
  * @param aNewTab The new tab where the referrer target opened, or null.