diff --git a/src/vs/workbench/api/electron-browser/mainThreadCommands.ts b/src/vs/workbench/api/electron-browser/mainThreadCommands.ts
index 4351231a41b0c721ebac95e29e2eda3833de2a7a..050e27b59d03c83b5f3a22cb7763c86ac42ef9eb 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadCommands.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadCommands.ts
@@ -9,6 +9,7 @@ import { IDisposable } from 'vs/base/common/lifecycle';
 import { TPromise } from 'vs/base/common/winjs.base';
 import { ExtHostContext, MainThreadCommandsShape, ExtHostCommandsShape, MainContext, IExtHostContext } from '../node/extHost.protocol';
 import { extHostNamedCustomer } from 'vs/workbench/api/electron-browser/extHostCustomers';
+import { revive } from 'vs/base/common/marshalling';
 
 @extHostNamedCustomer(MainContext.MainThreadCommands)
 export class MainThreadCommands implements MainThreadCommandsShape {
@@ -70,6 +71,9 @@ export class MainThreadCommands implements MainThreadCommandsShape {
 	}
 
 	$executeCommand<T>(id: string, args: any[]): Thenable<T> {
+		for (let i = 0; i < args.length; i++) {
+			args[i] = revive(args[i], 0);
+		}
 		return this._commandService.executeCommand<T>(id, ...args);
 	}
 
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index 0b7b069eab50d67f55b7dc5933e537a53bbb6129..ed498be9850d5b64fc681d5ec43b19ca83dd6acb 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -731,7 +731,7 @@ export interface ExtHostWindowShape {
 // --- proxy identifiers
 
 export const MainContext = {
-	MainThreadCommands: <ProxyIdentifier<MainThreadCommandsShape>>createMainId<MainThreadCommandsShape>('MainThreadCommands', ProxyType.CustomMarshaller),
+	MainThreadCommands: <ProxyIdentifier<MainThreadCommandsShape>>createMainId<MainThreadCommandsShape>('MainThreadCommands'),
 	MainThreadConfiguration: createMainId<MainThreadConfigurationShape>('MainThreadConfiguration', ProxyType.CustomMarshaller),
 	MainThreadDebugService: createMainId<MainThreadDebugServiceShape>('MainThreadDebugService', ProxyType.CustomMarshaller),
 	MainThreadDecorations: createMainId<MainThreadDecorationsShape>('MainThreadDecorations'),
@@ -761,7 +761,7 @@ export const MainContext = {
 };
 
 export const ExtHostContext = {
-	ExtHostCommands: createExtId<ExtHostCommandsShape>('ExtHostCommands', ProxyType.CustomMarshaller),
+	ExtHostCommands: createExtId<ExtHostCommandsShape>('ExtHostCommands'),
 	ExtHostConfiguration: createExtId<ExtHostConfigurationShape>('ExtHostConfiguration', ProxyType.CustomMarshaller),
 	ExtHostDiagnostics: createExtId<ExtHostDiagnosticsShape>('ExtHostDiagnostics'),
 	ExtHostDebugService: createExtId<ExtHostDebugServiceShape>('ExtHostDebugService', ProxyType.CustomMarshaller),
diff --git a/src/vs/workbench/api/node/extHostCommands.ts b/src/vs/workbench/api/node/extHostCommands.ts
index 1167a321ffcc73b77e5ea5866f01665b86531151..97ee3eb8232086d281a167f7c3657175321fd991 100644
--- a/src/vs/workbench/api/node/extHostCommands.ts
+++ b/src/vs/workbench/api/node/extHostCommands.ts
@@ -15,6 +15,7 @@ import { isFalsyOrEmpty } from 'vs/base/common/arrays';
 import * as modes from 'vs/editor/common/modes';
 import * as vscode from 'vscode';
 import { ILogService } from 'vs/platform/log/common/log';
+import { revive } from 'vs/base/common/marshalling';
 
 interface CommandHandler {
 	callback: Function;
@@ -28,18 +29,21 @@ export interface ArgumentProcessor {
 
 export class ExtHostCommands implements ExtHostCommandsShape {
 
-	private _commands = new Map<string, CommandHandler>();
-	private _proxy: MainThreadCommandsShape;
-	private _converter: CommandsConverter;
-	private _argumentProcessors: ArgumentProcessor[] = [];
+	private readonly _commands = new Map<string, CommandHandler>();
+	private readonly _proxy: MainThreadCommandsShape;
+	private readonly _converter: CommandsConverter;
+	private readonly _logService: ILogService;
+	private readonly _argumentProcessors: ArgumentProcessor[];
 
 	constructor(
 		mainContext: IMainContext,
 		heapService: ExtHostHeapService,
-		private logService: ILogService
+		logService: ILogService
 	) {
 		this._proxy = mainContext.getProxy(MainContext.MainThreadCommands);
 		this._converter = new CommandsConverter(this, heapService);
+		this._logService = logService;
+		this._argumentProcessors = [{ processArgument(a) { return revive(a, 0); } }];
 	}
 
 	get converter(): CommandsConverter {
@@ -51,7 +55,7 @@ export class ExtHostCommands implements ExtHostCommandsShape {
 	}
 
 	registerCommand(id: string, callback: <T>(...args: any[]) => T | Thenable<T>, thisArg?: any, description?: ICommandHandlerDescription): extHostTypes.Disposable {
-		this.logService.trace('ExtHostCommands#registerCommand', id);
+		this._logService.trace('ExtHostCommands#registerCommand', id);
 
 		if (!id.trim().length) {
 			throw new Error('invalid id');
@@ -72,12 +76,12 @@ export class ExtHostCommands implements ExtHostCommandsShape {
 	}
 
 	executeCommand<T>(id: string, ...args: any[]): Thenable<T> {
-		this.logService.trace('ExtHostCommands#executeCommand', id);
+		this._logService.trace('ExtHostCommands#executeCommand', id);
 
 		if (this._commands.has(id)) {
 			// we stay inside the extension host and support
 			// to pass any kind of parameters around
-			return this.$executeContributedCommand<T>(id, ...args);
+			return this._executeContributedCommand<T>(id, args);
 
 		} else {
 			// automagically convert some argument types
@@ -99,17 +103,10 @@ export class ExtHostCommands implements ExtHostCommandsShape {
 
 			return this._proxy.$executeCommand<T>(id, args);
 		}
-
 	}
 
-	$executeContributedCommand<T>(id: string, ...args: any[]): Thenable<T> {
-		let command = this._commands.get(id);
-		if (!command) {
-			return Promise.reject(new Error(`Contributed command '${id}' does not exist.`));
-		}
-
-		let { callback, thisArg, description } = command;
-
+	private _executeContributedCommand<T>(id: string, args: any[]): Thenable<T> {
+		let { callback, thisArg, description } = this._commands.get(id);
 		if (description) {
 			for (let i = 0; i < description.args.length; i++) {
 				try {
@@ -120,24 +117,26 @@ export class ExtHostCommands implements ExtHostCommandsShape {
 			}
 		}
 
-		args = args.map(arg => this._argumentProcessors.reduce((r, p) => p.processArgument(r), arg));
-
 		try {
 			let result = callback.apply(thisArg, args);
 			return Promise.resolve(result);
 		} catch (err) {
-			// console.log(err);
-			// try {
-			// 	console.log(toErrorMessage(err));
-			// } catch (err) {
-			// 	//
-			// }
+			this._logService.error(err, id);
 			return Promise.reject(new Error(`Running the contributed command:'${id}' failed.`));
 		}
 	}
 
+	$executeContributedCommand<T>(id: string, ...args: any[]): Thenable<T> {
+		if (!this._commands.has(id)) {
+			return Promise.reject(new Error(`Contributed command '${id}' does not exist.`));
+		} else {
+			args = args.map(arg => this._argumentProcessors.reduce((r, p) => p.processArgument(r), arg));
+			return this._executeContributedCommand(id, args);
+		}
+	}
+
 	getCommands(filterUnderscoreCommands: boolean = false): Thenable<string[]> {
-		this.logService.trace('ExtHostCommands#getCommands', filterUnderscoreCommands);
+		this._logService.trace('ExtHostCommands#getCommands', filterUnderscoreCommands);
 
 		return this._proxy.$getCommands().then(result => {
 			if (filterUnderscoreCommands) {