diff --git a/front_end/elements/ElementsPanel.js b/front_end/elements/ElementsPanel.js
index e0d3b8485d..9e84e816a6 100644
--- a/front_end/elements/ElementsPanel.js
+++ b/front_end/elements/ElementsPanel.js
@@ -96,7 +96,7 @@ export class ElementsPanel extends UI.Panel {
     self.Common.settings.moduleSetting('showUAShadowDOM').addChangeListener(this._showUAShadowDOMChanged.bind(this));
     self.SDK.targetManager.addModelListener(
         SDK.DOMModel, SDK.DOMModel.Events.DocumentUpdated, this._documentUpdatedEvent, this);
-    Extensions.extensionServer.addEventListener(
+    self.Extensions.extensionServer.addEventListener(
         Extensions.ExtensionServer.Events.SidebarPaneAdded, this._extensionSidebarPaneAdded, this);
 
     /**
@@ -813,7 +813,7 @@ export class ElementsPanel extends UI.Panel {
     }
     this._splitMode = splitMode;
 
-    const extensionSidebarPanes = Extensions.extensionServer.sidebarPanes();
+    const extensionSidebarPanes = self.Extensions.extensionServer.sidebarPanes();
     let lastSelectedTabId = null;
     if (this.sidebarPaneView) {
       lastSelectedTabId = this.sidebarPaneView.tabbedPane().selectedTabId;
diff --git a/front_end/extensions/ExtensionServer.js b/front_end/extensions/ExtensionServer.js
index 9877b7f84b..fcab89dbd1 100644
--- a/front_end/extensions/ExtensionServer.js
+++ b/front_end/extensions/ExtensionServer.js
@@ -723,7 +723,7 @@ export class ExtensionServer extends Common.Object {
         // See ExtensionAPI.js for details.
         const injectedAPI = self.buildExtensionAPIInjectedScript(
             extensionInfo, this._inspectedTabId, UI.themeSupport.themeName(),
-            self.UI.shortcutRegistry.globalShortcutKeys(), Extensions.extensionServer['_extensionAPITestHook']);
+            self.UI.shortcutRegistry.globalShortcutKeys(), self.Extensions.extensionServer['_extensionAPITestHook']);
         Host.InspectorFrontendHost.setInjectedScriptForOrigin(extensionOrigin, injectedAPI);
         this._registeredExtensions[extensionOrigin] = {name: name};
       }
diff --git a/front_end/extensions/ExtensionTraceProvider.js b/front_end/extensions/ExtensionTraceProvider.js
index 999621bd9b..bb28b6b832 100644
--- a/front_end/extensions/ExtensionTraceProvider.js
+++ b/front_end/extensions/ExtensionTraceProvider.js
@@ -24,11 +24,11 @@ export class ExtensionTraceProvider {
    */
   start(session) {
     const sessionId = String(++_lastSessionId);
-    Extensions.extensionServer.startTraceRecording(this._id, sessionId, session);
+    self.Extensions.extensionServer.startTraceRecording(this._id, sessionId, session);
   }
 
   stop() {
-    Extensions.extensionServer.stopTraceRecording(this._id);
+    self.Extensions.extensionServer.stopTraceRecording(this._id);
   }
 
   /**
diff --git a/front_end/extensions/extensions-legacy.js b/front_end/extensions/extensions-legacy.js
index 4c12c6aace..fbf5406a2d 100644
--- a/front_end/extensions/extensions-legacy.js
+++ b/front_end/extensions/extensions-legacy.js
@@ -34,4 +34,4 @@ Extensions.TracingSession = ExtensionsModule.ExtensionTraceProvider.TracingSessi
 Extensions.ExtensionStatus.Record;
 
 /** @type {!Extensions.ExtensionServer} */
-Extensions.extensionServer;
+self.Extensions.extensionServer;
diff --git a/front_end/extensions_test_runner/ExtensionsTestRunner.js b/front_end/extensions_test_runner/ExtensionsTestRunner.js
index afb172dd37..dc526abc6f 100644
--- a/front_end/extensions_test_runner/ExtensionsTestRunner.js
+++ b/front_end/extensions_test_runner/ExtensionsTestRunner.js
@@ -8,23 +8,23 @@
  */
 
 const extensionsHost = 'devtools-extensions.oopif.test';
-Extensions.extensionServer._registerHandler('evaluateForTestInFrontEnd', onEvaluate);
+self.Extensions.extensionServer._registerHandler('evaluateForTestInFrontEnd', onEvaluate);
 Extensions.extensionsOrigin = `http://${extensionsHost}:8000`;
-Extensions.extensionServer._extensionAPITestHook = function(extensionServerClient, coreAPI) {
+self.Extensions.extensionServer._extensionAPITestHook = function(extensionServerClient, coreAPI) {
   window.webInspector = coreAPI;
   window._extensionServerForTests = extensionServerClient;
   coreAPI.panels.themeName = 'themeNameForTest';
 };
 
 ExtensionsTestRunner._replyToExtension = function(requestId, port) {
-  Extensions.extensionServer._dispatchCallback(requestId, port);
+  self.Extensions.extensionServer._dispatchCallback(requestId, port);
 };
 
 function onEvaluate(message, port) {
   // Note: reply(...) is actually used in eval strings
   // eslint-disable-next-line no-unused-vars
   function reply(param) {
-    Extensions.extensionServer._dispatchCallback(message.requestId, port, param);
+    self.Extensions.extensionServer._dispatchCallback(message.requestId, port, param);
   }
 
   try {
@@ -58,7 +58,7 @@ ExtensionsTestRunner.runExtensionTests = async function(tests) {
   let extensionURL = pageURL.replace(/^(https?:\/\/[^\/]*\/).*$/, '$1') + 'devtools/resources/extension-main.html';
   extensionURL = extensionURL.replace('127.0.0.1', extensionsHost);
 
-  Extensions.extensionServer._addExtension(
+  self.Extensions.extensionServer._addExtension(
       {startPage: extensionURL, name: 'test extension', exposeWebInspectorNamespace: true});
 };
 
diff --git a/front_end/main/MainImpl.js b/front_end/main/MainImpl.js
index c9e85112c0..acd725939c 100644
--- a/front_end/main/MainImpl.js
+++ b/front_end/main/MainImpl.js
@@ -220,7 +220,7 @@ export class MainImpl {
         new Bindings.DebuggerWorkspaceBinding(self.SDK.targetManager, self.Workspace.workspace);
     self.Bindings.breakpointManager = new Bindings.BreakpointManager(
         self.Workspace.workspace, self.SDK.targetManager, self.Bindings.debuggerWorkspaceBinding);
-    Extensions.extensionServer = new Extensions.ExtensionServer();
+    self.Extensions.extensionServer = new Extensions.ExtensionServer();
 
     new Persistence.FileSystemWorkspaceBinding(self.Persistence.isolatedFileSystemManager, self.Workspace.workspace);
     self.Persistence.persistence =
@@ -304,7 +304,7 @@ export class MainImpl {
   _lateInitialization() {
     MainImpl.time('Main._lateInitialization');
     this._registerShortcuts();
-    Extensions.extensionServer.initializeExtensions();
+    self.Extensions.extensionServer.initializeExtensions();
     const extensions = self.runtime.extensions('late-initialization');
     const promises = [];
     for (const extension of extensions) {
diff --git a/front_end/sources/SourcesPanel.js b/front_end/sources/SourcesPanel.js
index 75dadcb315..fc3b64b162 100644
--- a/front_end/sources/SourcesPanel.js
+++ b/front_end/sources/SourcesPanel.js
@@ -134,7 +134,7 @@ export class SourcesPanel extends UI.Panel {
     self.SDK.targetManager.addModelListener(
         SDK.DebuggerModel, SDK.DebuggerModel.Events.GlobalObjectCleared,
         event => this._debuggerResumed(/** @type {!SDK.DebuggerModel} */ (event.data)));
-    Extensions.extensionServer.addEventListener(
+    self.Extensions.extensionServer.addEventListener(
         Extensions.ExtensionServer.Events.SidebarPaneAdded, this._extensionSidebarPaneAdded, this);
     self.SDK.targetManager.observeTargets(this);
   }
@@ -980,7 +980,7 @@ export class SourcesPanel extends UI.Panel {
     }
 
     this._sidebarPaneStack.appendApplicableItems('sources.sidebar-bottom');
-    const extensionSidebarPanes = Extensions.extensionServer.sidebarPanes();
+    const extensionSidebarPanes = self.Extensions.extensionServer.sidebarPanes();
     for (let i = 0; i < extensionSidebarPanes.length; ++i) {
       this._addExtensionSidebarPane(extensionSidebarPanes[i]);
     }
diff --git a/front_end/sources/TabbedEditorContainer.js b/front_end/sources/TabbedEditorContainer.js
index 37a8ce64fa..c0e7fb445a 100644
--- a/front_end/sources/TabbedEditorContainer.js
+++ b/front_end/sources/TabbedEditorContainer.js
@@ -266,7 +266,7 @@ export class TabbedEditorContainer extends Common.Object {
     this._history.updateSelectionRange(this._currentFile.url(), range);
     this._history.save(this._previouslyViewedFilesSetting);
 
-    Extensions.extensionServer.sourceSelectionChanged(this._currentFile.url(), range);
+    self.Extensions.extensionServer.sourceSelectionChanged(this._currentFile.url(), range);
   }
 
   /**
diff --git a/front_end/timeline/TimelineController.js b/front_end/timeline/TimelineController.js
index c19cc19a8d..ec99f07ad1 100644
--- a/front_end/timeline/TimelineController.js
+++ b/front_end/timeline/TimelineController.js
@@ -48,7 +48,7 @@ export class TimelineController {
    * @return {!Promise<!Object>}
    */
   async startRecording(options, providers) {
-    this._extensionTraceProviders = Extensions.extensionServer.traceProviders().slice();
+    this._extensionTraceProviders = self.Extensions.extensionServer.traceProviders().slice();
 
     /**
      * @param {string} category
diff --git a/front_end/timeline/TimelinePanel.js b/front_end/timeline/TimelinePanel.js
index 952cf52229..517fa69f55 100644
--- a/front_end/timeline/TimelinePanel.js
+++ b/front_end/timeline/TimelinePanel.js
@@ -131,7 +131,7 @@ export class TimelinePanel extends UI.Panel {
     this._showLandingPage();
     this._updateTimelineControls();
 
-    Extensions.extensionServer.addEventListener(
+    self.Extensions.extensionServer.addEventListener(
         Extensions.ExtensionServer.Events.TraceProviderAdded, this._appendExtensionsToToolbar, this);
     self.SDK.targetManager.addEventListener(
         SDK.TargetManager.Events.SuspendStateChanged, this._onSuspendStateChanged, this);
@@ -535,7 +535,7 @@ export class TimelinePanel extends UI.Panel {
 
     this._showRecordingStarted();
 
-    const enabledTraceProviders = Extensions.extensionServer.traceProviders().filter(
+    const enabledTraceProviders = self.Extensions.extensionServer.traceProviders().filter(
         provider => TimelinePanel._settingForTraceProvider(provider).get());
 
     const mainTarget = /** @type {!SDK.Target} */ (self.SDK.targetManager.mainTarget());