diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index 0e6822072e3..0eb129114bc 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -255,18 +255,6 @@ export function createApiFactory(initData: IInitData, threadService: IThreadServ
 			}
 		};
 
-		const emptyMessageOptions: vscode.MessageOptions = Object.create(null);
-
-		function parseMessageArguments(args: any[]): { options: vscode.MessageOptions; items: any[]; } {
-			const [first, ...rest] = args;
-
-			if (typeof first === 'string' || (first && first.title)) {
-				return { options: emptyMessageOptions, items: args };
-			} else {
-				return { options: first || emptyMessageOptions, items: rest };
-			}
-		}
-
 		// namespace: window
 		const window: typeof vscode.window = {
 			get activeTextEditor() {
@@ -299,17 +287,14 @@ export function createApiFactory(initData: IInitData, threadService: IThreadServ
 			onDidCloseTerminal(listener, thisArg?, disposables?) {
 				return extHostTerminalService.onDidCloseTerminal(listener, thisArg, disposables);
 			},
-			showInformationMessage(message, ...args) {
-				const { options, items } = parseMessageArguments(args);
-				return extHostMessageService.showMessage(Severity.Info, message, options, items);
+			showInformationMessage(message, first, ...rest) {
+				return extHostMessageService.showMessage(Severity.Info, message, first, rest);
 			},
-			showWarningMessage(message, ...args) {
-				const { options, items } = parseMessageArguments(args);
-				return extHostMessageService.showMessage(Severity.Warning, message, options, items);
+			showWarningMessage(message, first, ...rest) {
+				return extHostMessageService.showMessage(Severity.Warning, message, first, rest);
 			},
-			showErrorMessage(message, ...args) {
-				const { options, items } = parseMessageArguments(args);
-				return extHostMessageService.showMessage(Severity.Error, message, options, items);
+			showErrorMessage(message, first, ...rest) {
+				return extHostMessageService.showMessage(Severity.Error, message, first, rest);
 			},
 			showQuickPick(items: any, options: vscode.QuickPickOptions, token?: vscode.CancellationToken) {
 				return extHostQuickOpen.showQuickPick(items, options, token);
diff --git a/src/vs/workbench/api/node/extHostMessageService.ts b/src/vs/workbench/api/node/extHostMessageService.ts
index b02a13f349c..20817326501 100644
--- a/src/vs/workbench/api/node/extHostMessageService.ts
+++ b/src/vs/workbench/api/node/extHostMessageService.ts
@@ -9,6 +9,20 @@ import Severity from 'vs/base/common/severity';
 import vscode = require('vscode');
 import { MainContext, MainThreadMessageServiceShape } from './extHost.protocol';
 
+const emptyMessageOptions: vscode.MessageOptions = Object.create(null);
+
+function isMessageItem<T>(item: any): item is vscode.MessageItem {
+	return item && item.title;
+}
+
+function parseMessageArguments(first: vscode.MessageOptions | string | vscode.MessageItem, rest: (string | vscode.MessageItem)[]): { options: vscode.MessageOptions; items: (string | vscode.MessageItem)[]; } {
+	if (typeof first === 'string' || isMessageItem(first)) {
+		return { options: emptyMessageOptions, items: [first, ...rest] };
+	} else {
+		return { options: first || emptyMessageOptions, items: rest };
+	}
+}
+
 export class ExtHostMessageService {
 
 	private _proxy: MainThreadMessageServiceShape;
@@ -17,25 +31,25 @@ export class ExtHostMessageService {
 		this._proxy = threadService.get(MainContext.MainThreadMessageService);
 	}
 
-	showMessage(severity: Severity, message: string, options: vscode.MessageOptions, commands: (string | vscode.MessageItem)[]): Thenable<string | vscode.MessageItem> {
+	showMessage(severity: Severity, message: string, optionsOrFirstItem: vscode.MessageOptions | string | vscode.MessageItem, rest: (string | vscode.MessageItem)[]): Thenable<string | vscode.MessageItem> {
+		const { options, items } = parseMessageArguments(optionsOrFirstItem, rest);
+		const commands: { title: string; isCloseAffordance: boolean; handle: number; }[] = [];
 
-		const items: { title: string; isCloseAffordance: boolean; handle: number; }[] = [];
-
-		for (let handle = 0; handle < commands.length; handle++) {
-			let command = commands[handle];
+		for (let handle = 0; handle < items.length; handle++) {
+			let command = items[handle];
 			if (typeof command === 'string') {
-				items.push({ title: command, handle, isCloseAffordance: false });
+				commands.push({ title: command, handle, isCloseAffordance: false });
 			} else if (typeof command === 'object') {
 				let {title, isCloseAffordance} = command;
-				items.push({ title, isCloseAffordance, handle });
+				commands.push({ title, isCloseAffordance, handle });
 			} else {
 				console.warn('Invalid message item:', command);
 			}
 		}
 
-		return this._proxy.$showMessage(severity, message, options, items).then(handle => {
+		return this._proxy.$showMessage(severity, message, options, commands).then(handle => {
 			if (typeof handle === 'number') {
-				return commands[handle];
+				return items[handle];
 			}
 		});
 	}