diff --git a/dom/security/test/mixedcontentblocker/test_frameNavigation.html b/dom/security/test/mixedcontentblocker/test_frameNavigation.html
index 3ee7b3876515..5b3ae50b0761 100644
--- a/dom/security/test/mixedcontentblocker/test_frameNavigation.html
+++ b/dom/security/test/mixedcontentblocker/test_frameNavigation.html
@@ -90,12 +90,12 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=840388
     switch(event.data.test) {
 
       case "insecurePage_navigate_child":
-        ok((event.data.msg == "navigated to insecure iframe on insecure page"), "navigating to insecure iframe blocked on insecure page");
+        is(event.data.msg, "navigated to insecure iframe on insecure page", "navigating to insecure iframe blocked on insecure page");
         testsToRunInsecure["insecurePage_navigate_child"] = true;
         break;
 
       case "insecurePage_navigate_grandchild":
-        ok((event.data.msg == "navigated to insecure grandchild iframe on insecure page"), "navigating to insecure grandchild iframe blocked on insecure page");
+        is(event.data.msg, "navigated to insecure grandchild iframe on insecure page", "navigating to insecure grandchild iframe blocked on insecure page");
         testsToRunInsecure["insecurePage_navigate_grandchild"] = true;
         break;
 
@@ -105,7 +105,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=840388
         break;
 
       case "blankTarget":
-        ok((event.data.msg == "opened an http link with target=_blank from a secure page"), "couldn't open an http link in a new window from a secure page");
+        is(event.data.msg, "opened an http link with target=_blank from a secure page", "couldn't open an http link in a new window from a secure page");
         testsToRunSecure["blankTarget"] = true;
         break;