diff --git a/src/vs/workbench/api/electron-browser/mainThreadExtensionService.ts b/src/vs/workbench/api/browser/mainThreadExtensionService.ts
similarity index 96%
rename from src/vs/workbench/api/electron-browser/mainThreadExtensionService.ts
rename to src/vs/workbench/api/browser/mainThreadExtensionService.ts
index 1d0480e92e0c17b8ec4ed43a9df174312f84edc4..4d91e90252e8022d5a268219bea4a6b950151e52 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadExtensionService.ts
+++ b/src/vs/workbench/api/browser/mainThreadExtensionService.ts
@@ -8,7 +8,6 @@ import Severity from 'vs/base/common/severity';
 import { extHostNamedCustomer } from 'vs/workbench/api/common/extHostCustomers';
 import { IExtHostContext, MainContext, MainThreadExtensionServiceShape } from 'vs/workbench/api/common/extHost.protocol';
 import { IExtensionService, ExtensionActivationError } from 'vs/workbench/services/extensions/common/extensions';
-import { ExtensionService } from 'vs/workbench/services/extensions/electron-browser/extensionService';
 import { ExtensionIdentifier, IExtensionDescription } from 'vs/platform/extensions/common/extensions';
 import { INotificationService } from 'vs/platform/notification/common/notification';
 import { localize } from 'vs/nls';
@@ -21,7 +20,7 @@ import { IExtensionsWorkbenchService, IExtension } from 'vs/workbench/contrib/ex
 @extHostNamedCustomer(MainContext.MainThreadExtensionService)
 export class MainThreadExtensionService implements MainThreadExtensionServiceShape {
 
-	private readonly _extensionService: ExtensionService;
+	private readonly _extensionService: IExtensionService;
 	private readonly _notificationService: INotificationService;
 	private readonly _extensionsWorkbenchService: IExtensionsWorkbenchService;
 	private readonly _windowService: IWindowService;
@@ -33,9 +32,7 @@ export class MainThreadExtensionService implements MainThreadExtensionServiceSha
 		@IExtensionsWorkbenchService extensionsWorkbenchService: IExtensionsWorkbenchService,
 		@IWindowService windowService: IWindowService
 	) {
-		if (extensionService instanceof ExtensionService) {
-			this._extensionService = extensionService;
-		}
+		this._extensionService = extensionService;
 		this._notificationService = notificationService;
 		this._extensionsWorkbenchService = extensionsWorkbenchService;
 		this._windowService = windowService;
diff --git a/src/vs/workbench/api/electron-browser/extensionHost.contribution.ts b/src/vs/workbench/api/electron-browser/extensionHost.contribution.ts
index cf892571e2d591f17cd4d1ad361921e8e4cea15e..dc8b0de40d4cd7cc7b9c9453470c559923ac6dd7 100644
--- a/src/vs/workbench/api/electron-browser/extensionHost.contribution.ts
+++ b/src/vs/workbench/api/electron-browser/extensionHost.contribution.ts
@@ -50,7 +50,7 @@ import '../browser/mainThreadWindow';
 import '../browser/mainThreadWorkspace';
 import './mainThreadComments';
 import './mainThreadConsole';
-import './mainThreadExtensionService';
+import '../browser/mainThreadExtensionService';
 import './mainThreadTask';
 import './mainThreadWebview';
 import 'vs/workbench/api/node/apiCommands';
diff --git a/src/vs/workbench/services/extensions/common/extensions.ts b/src/vs/workbench/services/extensions/common/extensions.ts
index 04a24e602ce8aae3da8980a7dddae61fc80d2a80..107d91e721ee25fa11361b38e51576a558e447a1 100644
--- a/src/vs/workbench/services/extensions/common/extensions.ts
+++ b/src/vs/workbench/services/extensions/common/extensions.ts
@@ -218,6 +218,13 @@ export interface IExtensionService extends ICpuProfilerTarget {
 	 * Stops the extension host.
 	 */
 	stopExtensionHost(): void;
+
+	_logOrShowMessage(severity: Severity, msg: string): void;
+	_activateById(extensionId: ExtensionIdentifier, activationEvent: string): Promise<void>;
+	_onWillActivateExtension(extensionId: ExtensionIdentifier): void;
+	_onDidActivateExtension(extensionId: ExtensionIdentifier, startup: boolean, codeLoadingTime: number, activateCallTime: number, activateResolvedTime: number, activationEvent: string): void;
+	_onExtensionRuntimeError(extensionId: ExtensionIdentifier, err: Error): void;
+
 }
 
 export interface ICpuProfilerTarget {
@@ -278,4 +285,9 @@ export class NullExtensionService implements IExtensionService {
 	stopExtensionHost(): void { }
 	canAddExtension(): boolean { return false; }
 	canRemoveExtension(): boolean { return false; }
-}
\ No newline at end of file
+	_logOrShowMessage(_severity: Severity, _msg: string): void { }
+	_activateById(_extensionId: ExtensionIdentifier, _activationEvent: string): Promise<void> { return Promise.resolve(); }
+	_onWillActivateExtension(_extensionId: ExtensionIdentifier): void { }
+	_onDidActivateExtension(_extensionId: ExtensionIdentifier, _startup: boolean, _codeLoadingTime: number, _activateCallTime: number, _activateResolvedTime: number, _activationEvent: string): void { }
+	_onExtensionRuntimeError(_extensionId: ExtensionIdentifier, _err: Error): void { }
+}