diff --git a/dom/manifest/ManifestProcessor.jsm b/dom/manifest/ManifestProcessor.jsm
index d9e39ac4d337..ef7e2bdd99b9 100644
--- a/dom/manifest/ManifestProcessor.jsm
+++ b/dom/manifest/ManifestProcessor.jsm
@@ -101,14 +101,18 @@ ManifestProcessor.prototype = {
   //  * manifestURL: the URL of the manifest, to resolve URLs.
   //  * docURL: the URL of the owner doc, for security checks.
   process({
-    jsonText, manifestURL, docURL
+    jsonText: aJsonText,
+    manifestURL: aManifestURL,
+    docURL: aDocURL
   }) {
+    const manifestURL = new URL(aManifestURL);
+    const docURL = new URL(aDocURL);
     const console = new ConsoleAPI({
       prefix: 'Web Manifest: '
     });
     let rawManifest = {};
     try {
-      rawManifest = JSON.parse(jsonText);
+      rawManifest = JSON.parse(aJsonText);
     } catch (e) {}
     if (typeof rawManifest !== 'object' || rawManifest === null) {
       let msg = 'Manifest needs to be an object.';
@@ -124,7 +128,8 @@ ManifestProcessor.prototype = {
       short_name: processShortNameMember(rawManifest),
     };
     processedManifest.scope = processScopeMember(rawManifest, manifestURL,
-      docURL, processedManifest.start_url);
+      docURL, new URL(processedManifest.start_url));
+
     return processedManifest;
 
     function processNameMember(aManifest) {
@@ -188,8 +193,11 @@ ManifestProcessor.prototype = {
         expectedType: 'string',
         trim: false
       };
-      const value = extractValue(spec, console);
       let scopeURL;
+      const value = extractValue(spec, console);
+      if (value === undefined || value === '') {
+        return undefined;
+      }
       try {
         scopeURL = new URL(value, aManifestURL);
       } catch (e) {
@@ -210,7 +218,7 @@ ManifestProcessor.prototype = {
         console.warn(msg);
         return undefined;
       }
-      return scopeURL;
+      return scopeURL.href;
     }
 
     function processStartURLMember(aManifest, aManifestURL, aDocURL) {
@@ -221,7 +229,7 @@ ManifestProcessor.prototype = {
         expectedType: 'string',
         trim: false
       };
-      let result = new URL(aDocURL);
+      let result = new URL(aDocURL).href;
       const value = extractValue(spec, console);
       if (value === undefined || value === '') {
         return result;
@@ -237,7 +245,7 @@ ManifestProcessor.prototype = {
         let msg = 'start_url must be same origin as document.';
         console.warn(msg);
       } else {
-        result = potentialResult;
+        result = potentialResult.href;
       }
       return result;
     }
@@ -248,7 +256,7 @@ this.ManifestProcessor = ManifestProcessor;
 function IconsProcessor() {}
 
 // Static getters
-Object.defineProperties(IconsProcessor,{
+Object.defineProperties(IconsProcessor, {
   'onlyDecimals': {
     get: function() {
       return /^\d+$/;
@@ -324,7 +332,7 @@ IconsProcessor.process = function(aManifest, aBaseURL, console) {
     let url;
     if (value && value.length) {
       try {
-        url = new URL(value, aBaseURL);
+        url = new URL(value, aBaseURL).href;
       } catch (e) {}
     }
     return url;
diff --git a/dom/manifest/test/mochitest.ini b/dom/manifest/test/mochitest.ini
index 87fe83a9cab1..de725fe96087 100644
--- a/dom/manifest/test/mochitest.ini
+++ b/dom/manifest/test/mochitest.ini
@@ -1,5 +1,4 @@
 [DEFAULT]
-skip-if = e10s
 
 support-files =
 	common.js
diff --git a/dom/manifest/test/test_IconsProcessor_src.html b/dom/manifest/test/test_IconsProcessor_src.html
index 3b298be126ea..7bf0f58a1534 100644
--- a/dom/manifest/test/test_IconsProcessor_src.html
+++ b/dom/manifest/test/test_IconsProcessor_src.html
@@ -61,7 +61,7 @@ data.jsonText = JSON.stringify(noSrc);
 var result = processor.process(data);
 ise(result.icons.length, 0, expected);
 
-var expected = `Expect icon's src to be an instance of URL.`;
+var expected = `Expect icon's src to be a string.`;
 var withSrc = {
   icons: [{
     src: 'pass'
@@ -69,7 +69,7 @@ var withSrc = {
 };
 data.jsonText = JSON.stringify(withSrc);
 var result = processor.process(data);
-ise(SpecialPowers.unwrap(result.icons[0].src) instanceof URL, true, expected);
+ise(typeof result.icons[0].src, "string", expected);
 
 var expected = `Expect only icons with a src prop to be kept.`;
 var withSrc = {
diff --git a/dom/manifest/test/test_ManifestProcessor_JSON.html b/dom/manifest/test/test_ManifestProcessor_JSON.html
index 90bfcba0c362..419504000764 100644
--- a/dom/manifest/test/test_ManifestProcessor_JSON.html
+++ b/dom/manifest/test/test_ManifestProcessor_JSON.html
@@ -20,7 +20,7 @@ invalidJson.forEach((testString) => {
   var expected = `Expect to recover from invalid JSON: ${testString}`;
   data.jsonText = testString;
   var result = processor.process(data);
-  SimpleTest.ok(result.start_url.href === docURL.href, true, expected);
+  SimpleTest.ise(result.start_url, docURL.href, expected);
 });
 
 var validButUnhelpful = ["1", 1, "", "[{}]", "null"];
@@ -28,7 +28,7 @@ validButUnhelpful.forEach((testString) => {
   var expected = `Expect to recover from invalid JSON: ${testString}`;
   data.jsonText = testString;
   var result = processor.process(data);
-  SimpleTest.ok(result.start_url.href === docURL.href, true, expected);
+  SimpleTest.ise(result.start_url, docURL.href, expected);
 });
   </script>
 </head>
diff --git a/dom/manifest/test/test_ManifestProcessor_scope.html b/dom/manifest/test/test_ManifestProcessor_scope.html
index 51badd7daa9c..ef23998cd25a 100644
--- a/dom/manifest/test/test_ManifestProcessor_scope.html
+++ b/dom/manifest/test/test_ManifestProcessor_scope.html
@@ -47,8 +47,7 @@ URLs.forEach((url) => {
   });
   var absURL = new URL(url, manifestURL).toString();
   var result = processor.process(data);
-  console.log(result);
-  ise(String(result.scope), absURL, expected);
+  ise(result.scope, absURL, expected);
 });
 
 var expected = 'If start URL is not in scope, return undefined.';