--- a/b2g/components/ProcessGlobal.js
+++ b/b2g/components/ProcessGlobal.js
@@ -102,16 +102,17 @@ ProcessGlobal.prototype = {
       if (params[0] == "wipe") {
         this.wipeDir(params[1]);
       } else if (params[0] == "root") {
         log("unrestrict devtools");
         Services.prefs.setBoolPref("devtools.debugger.forbid-certified-apps", false);
         Services.prefs.setBoolPref("dom.apps.developer_mode", true);
         // TODO: Remove once bug 1125916 is fixed.
         Services.prefs.setBoolPref("network.disable.ipc.security", true);
+        Services.prefs.setBoolPref("dom.webcomponents.enabled", true);
         let lock = settings.createLock();
         lock.set("developer.menu.enabled", true, null);
       }
     });
   },
 
   cleanupAfterFactoryReset: function() {
     log("cleanupAfterWipe start");

--- a/browser/devtools/webide/content/runtimedetails.js
+++ b/browser/devtools/webide/content/runtimedetails.js
@@ -137,16 +137,17 @@ function EnableCertApps() {
   let device = AppManager.selectedRuntime.device;
   // TODO: Remove `network.disable.ipc.security` once bug 1125916 is fixed.
   device.shell(
     "stop b2g && " +
     "cd /data/b2g/mozilla/*.default/ && " +
     "echo 'user_pref(\"devtools.debugger.forbid-certified-apps\", false);' >> prefs.js && " +
     "echo 'user_pref(\"dom.apps.developer_mode\", true);' >> prefs.js && " +
     "echo 'user_pref(\"network.disable.ipc.security\", true);' >> prefs.js && " +
+    "echo 'user_pref(\"dom.webcomponents.enabled\", true);' >> prefs.js && " +
     "start b2g"
   );
 }
 
 function RootADB() {
   let device = AppManager.selectedRuntime.device;
   device.summonRoot().then(CheckLockState, (e) => console.error(e));
 }