--- a/browser/components/extensions/test/browser/browser_ext_webNavigation_getFrames.js
+++ b/browser/components/extensions/test/browser/browser_ext_webNavigation_getFrames.js
@@ -134,17 +134,21 @@ add_task(function* testWebNavigationFram
     getFrameResults,
   } = yield extension.awaitMessage("webNavigationFrames.done");
 
   is(getAllFramesDetails.length, 3, "expected number of frames found");
   is(getAllFramesDetails.length, collectedDetails.length,
      "number of frames found should equal the number onCompleted events collected");
 
   // ordered by frameId
-  let sortByFrameId = (el) => el ? el.frameId : -1;
+  let sortByFrameId = (el1, el2) => {
+    let val1 = el1 ? el1.frameId : -1;
+    let val2 = el2 ? el2.frameId : -1;
+    return val1 - val2;
+  };
 
   collectedDetails = collectedDetails.sort(sortByFrameId);
   getAllFramesDetails = getAllFramesDetails.sort(sortByFrameId);
   getFrameResults = getFrameResults.sort(sortByFrameId);
 
   info("check frame details content");
 
   is(getFrameResults.length, getAllFramesDetails.length,