--- a/devtools/client/inspector/inspector.js
+++ b/devtools/client/inspector/inspector.js
@@ -5,16 +5,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* global window, BrowserLoader */
 
 "use strict";
 
 const Services = require("Services");
 const promise = require("promise");
+const flags = require("devtools/shared/flags");
 const EventEmitter = require("devtools/shared/event-emitter");
 const {executeSoon} = require("devtools/shared/DevToolsUtils");
 const {Toolbox} = require("devtools/client/framework/toolbox");
 const ReflowTracker = require("devtools/client/inspector/shared/reflow-tracker");
 const Store = require("devtools/client/inspector/store");
 const InspectorStyleChangeTracker = require("devtools/client/inspector/shared/style-change-tracker");
 
 // Use privileged promise in panel documents to prevent having them to freeze
@@ -286,17 +287,20 @@ Inspector.prototype = {
     // We can display right panel with: tab bar, markup view and breadbrumb. Right after
     // the splitter set the right and left panel sizes, in order to avoid resizing it
     // during load of the inspector.
     this.panelDoc.getElementById("inspector-main-content").style.visibility = "visible";
 
     // Setup the sidebar panels.
     this.setupSidebar();
 
-    await this.once("markuploaded");
+    if (flags.testing) {
+      await this.once("markuploaded");
+    }
+
     this.isReady = true;
 
     // All the components are initialized. Take care of the remaining initialization
     // and setup.
     this.breadcrumbs = new HTMLBreadcrumbs(this);
     this.setupExtensionSidebars();
     this.setupSearchBox();
     await this.setupToolbar();