diff --git a/src/vs/workbench/api/common/extHostExtensionService.ts b/src/vs/workbench/api/common/extHostExtensionService.ts
index 99553033cd2..8c903a6027c 100644
--- a/src/vs/workbench/api/common/extHostExtensionService.ts
+++ b/src/vs/workbench/api/common/extHostExtensionService.ts
@@ -5,7 +5,7 @@
 
 import * as nls from 'vs/nls';
 import * as path from 'vs/base/common/path';
-import { originalFSPath } from 'vs/base/common/resources';
+import { originalFSPath, joinPath } from 'vs/base/common/resources';
 import { Barrier } from 'vs/base/common/async';
 import { dispose, toDisposable, DisposableStore } from 'vs/base/common/lifecycle';
 import { TernarySearchTree } from 'vs/base/common/map';
@@ -332,14 +332,14 @@ export abstract class AbstractExtHostExtensionService implements ExtHostExtensio
 
 		const activationTimesBuilder = new ExtensionActivationTimesBuilder(reason.startup);
 		return Promise.all<any>([
-			this._loadCommonJSModule(extensionDescription.main, activationTimesBuilder),
+			this._loadCommonJSModule(joinPath(extensionDescription.extensionLocation, extensionDescription.main), activationTimesBuilder),
 			this._loadExtensionContext(extensionDescription)
 		]).then(values => {
 			return AbstractExtHostExtensionService._callActivate(this._logService, extensionDescription.identifier, <IExtensionModule>values[0], <IExtensionContext>values[1], activationTimesBuilder);
 		});
 	}
 
-	protected abstract _loadCommonJSModule<T>(modulePath: string, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T>;
+	protected abstract _loadCommonJSModule<T>(module: URI, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T>;
 
 	private _loadExtensionContext(extensionDescription: IExtensionDescription): Promise<vscode.ExtensionContext> {
 
@@ -536,7 +536,7 @@ export abstract class AbstractExtHostExtensionService implements ExtHostExtensio
 		let testRunner: ITestRunner | INewTestRunner | undefined;
 		let requireError: Error | undefined;
 		try {
-			testRunner = await this._loadCommonJSModule(extensionTestsPath, new ExtensionActivationTimesBuilder(false));
+			testRunner = await this._loadCommonJSModule(URI.file(extensionTestsPath), new ExtensionActivationTimesBuilder(false));
 		} catch (error) {
 			requireError = error;
 		}
diff --git a/src/vs/workbench/api/node/extHostExtensionService.ts b/src/vs/workbench/api/node/extHostExtensionService.ts
index 8f1f5d6ee75..5b03a318564 100644
--- a/src/vs/workbench/api/node/extHostExtensionService.ts
+++ b/src/vs/workbench/api/node/extHostExtensionService.ts
@@ -11,6 +11,8 @@ import { connectProxyResolver } from 'vs/workbench/services/extensions/node/prox
 import { AbstractExtHostExtensionService } from 'vs/workbench/api/common/extHostExtensionService';
 import { ExtHostDownloadService } from 'vs/workbench/api/node/extHostDownloadService';
 import { CLIServer } from 'vs/workbench/api/node/extHostCLIServer';
+import { URI } from 'vs/base/common/uri';
+import { Schemas } from 'vs/base/common/network';
 
 export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 
@@ -55,12 +57,15 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 		};
 	}
 
-	protected _loadCommonJSModule<T>(modulePath: string, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T> {
+	protected _loadCommonJSModule<T>(module: URI, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T> {
+		if (module.scheme !== Schemas.file) {
+			throw new Error(`Cannot load URI: '${module}', must be of file-scheme`);
+		}
 		let r: T | null = null;
 		activationTimesBuilder.codeLoadingStart();
-		this._logService.info(`ExtensionService#loadCommonJSModule ${modulePath}`);
+		this._logService.info(`ExtensionService#loadCommonJSModule ${module.toString(true)}`);
 		try {
-			r = require.__$__nodeRequire<T>(modulePath);
+			r = require.__$__nodeRequire<T>(module.fsPath);
 		} catch (e) {
 			return Promise.reject(e);
 		} finally {
diff --git a/src/vs/workbench/api/worker/extHostExtensionService.ts b/src/vs/workbench/api/worker/extHostExtensionService.ts
index be34dbe2d64..19b44f7dc18 100644
--- a/src/vs/workbench/api/worker/extHostExtensionService.ts
+++ b/src/vs/workbench/api/worker/extHostExtensionService.ts
@@ -54,11 +54,11 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 		this._apiInstances = new ApiInstances(apiFactory, extensionPath, this._registry, configProvider);
 	}
 
-	protected _loadCommonJSModule<T>(modulePath: string, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T> {
+	protected _loadCommonJSModule<T>(module: URI, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T> {
 
 		// make sure modulePath ends with `.js`
 		const suffix = '.js';
-		modulePath = endsWith(modulePath, suffix) ? modulePath : modulePath + suffix;
+		let modulePath = endsWith(module.fsPath, suffix) ? module.fsPath : module.fsPath + suffix;
 
 		interface FakeCommonJSSelf {
 			module?: object;
@@ -71,9 +71,9 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 
 		// FAKE commonjs world that only collects exports
 		const patchSelf: FakeCommonJSSelf = <any>self;
-		const module = { exports: {} };
-		patchSelf.module = module;
-		patchSelf.exports = module.exports;
+		const exports = Object.create(null);
+		patchSelf.module = { exports };
+		patchSelf.exports = exports;
 		patchSelf.window = self; // <- that's improper but might help extensions that aren't authored correctly
 
 		// FAKE require function that only works for the vscode-module
@@ -97,7 +97,7 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 			activationTimesBuilder.codeLoadingStop();
 		}
 
-		return Promise.resolve(module.exports as T);
+		return Promise.resolve<T>(exports);
 	}
 
 	async $setRemoteEnvironment(env: { [key: string]: string | null }): Promise<void> {
diff --git a/src/vs/workbench/services/extensions/node/extensionPoints.ts b/src/vs/workbench/services/extensions/node/extensionPoints.ts
index f20f824a2e2..8abe6aa7f52 100644
--- a/src/vs/workbench/services/extensions/node/extensionPoints.ts
+++ b/src/vs/workbench/services/extensions/node/extensionPoints.ts
@@ -309,11 +309,6 @@ class ExtensionManifestValidator extends ExtensionManifestHandler {
 		extensionDescription.id = `${extensionDescription.publisher}.${extensionDescription.name}`;
 		extensionDescription.identifier = new ExtensionIdentifier(extensionDescription.id);
 
-		// main := absolutePath(`main`)
-		if (extensionDescription.main) {
-			extensionDescription.main = path.join(this._absoluteFolderPath, extensionDescription.main);
-		}
-
 		extensionDescription.extensionLocation = URI.file(this._absoluteFolderPath);
 
 		return extensionDescription;