diff --git a/browser/components/places/tests/browser/browser_423515.js b/browser/components/places/tests/browser/browser_423515.js
index f925853ee0d..1af52d7b940 100644
--- a/browser/components/places/tests/browser/browser_423515.js
+++ b/browser/components/places/tests/browser/browser_423515.js
@@ -152,7 +152,7 @@ function test() {
           }
         }
         node.containerOpen = false;
-        throw("Unable to find child node");
+        ok(false, "Unable to find child node");
         return null;
       }
 
diff --git a/browser/components/sessionstore/test/browser/browser_394759_privatebrowsing.js b/browser/components/sessionstore/test/browser/browser_394759_privatebrowsing.js
index 76f5c741e9f..cd01dbde25a 100644
--- a/browser/components/sessionstore/test/browser/browser_394759_privatebrowsing.js
+++ b/browser/components/sessionstore/test/browser/browser_394759_privatebrowsing.js
@@ -79,7 +79,7 @@ let pass = 0;
 const MAX_PASS = 6;
 function waitForSessionStoreJS() {
   if (++pass > MAX_PASS) {
-    throw("Timed out waiting for sessionstore.js");
+    ok(false, "Timed out waiting for sessionstore.js");
     finish();
   }
 
diff --git a/browser/components/sessionstore/test/browser/browser_459906.js b/browser/components/sessionstore/test/browser/browser_459906.js
index 296af2e9736..3e8d282d02a 100644
--- a/browser/components/sessionstore/test/browser/browser_459906.js
+++ b/browser/components/sessionstore/test/browser/browser_459906.js
@@ -69,7 +69,7 @@ function test() {
         let iframes = tab2.linkedBrowser.contentWindow.frames;
         if (iframes[1].document.body.innerHTML != uniqueValue &&
             ++pass <= MAX_PASS) {
-          SetTimeout(500, arguments.callee);
+          setTimeout(500, arguments.callee);
           return;
         }
         is(iframes[1].document.body.innerHTML, uniqueValue,