diff --git a/src/vs/workbench/api/electron-browser/mainThreadTreeViews.ts b/src/vs/workbench/api/electron-browser/mainThreadTreeViews.ts
index 6c3229615ef..0b909bd4ba7 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadTreeViews.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadTreeViews.ts
@@ -98,13 +98,13 @@ class TreeViewDataProvider implements ITreeViewDataProvider {
 		if (treeItem && treeItem.children) {
 			return TPromise.as(treeItem.children);
 		}
-		return this._proxy.$getChildren(this.treeViewId, treeItem ? treeItem.handle : void 0)
+		return TPromise.wrap(this._proxy.$getChildren(this.treeViewId, treeItem ? treeItem.handle : void 0)
 			.then(children => {
 				return this.postGetChildren(children);
 			}, err => {
 				this.notificationService.error(err);
 				return [];
-			});
+			}));
 	}
 
 	getItemsToRefresh(itemsToRefreshByHandle: { [treeItemHandle: string]: ITreeItem }): ITreeItem[] {
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index c38fd882d4e..8c7eb815e2d 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -206,7 +206,7 @@ export interface MainThreadTextEditorsShape extends IDisposable {
 
 export interface MainThreadTreeViewsShape extends IDisposable {
 	$registerTreeViewDataProvider(treeViewId: string): void;
-	$refresh(treeViewId: string, itemsToRefresh?: { [treeItemHandle: string]: ITreeItem }): TPromise<void>;
+	$refresh(treeViewId: string, itemsToRefresh?: { [treeItemHandle: string]: ITreeItem }): Thenable<void>;
 	$reveal(treeViewId: string, treeItem: ITreeItem, parentChain: ITreeItem[], options: { select: boolean, focus: boolean }): Thenable<void>;
 }
 
@@ -667,7 +667,7 @@ export interface ExtHostDocumentsAndEditorsShape {
 }
 
 export interface ExtHostTreeViewsShape {
-	$getChildren(treeViewId: string, treeItemHandle?: string): TPromise<ITreeItem[]>;
+	$getChildren(treeViewId: string, treeItemHandle?: string): Thenable<ITreeItem[]>;
 	$setExpanded(treeViewId: string, treeItemHandle: string, expanded: boolean): void;
 	$setSelection(treeViewId: string, treeItemHandles: string[]): void;
 	$setVisible(treeViewId: string, visible: boolean): void;
diff --git a/src/vs/workbench/api/node/extHostTreeViews.ts b/src/vs/workbench/api/node/extHostTreeViews.ts
index d39894bb57c..af5b5fd47e2 100644
--- a/src/vs/workbench/api/node/extHostTreeViews.ts
+++ b/src/vs/workbench/api/node/extHostTreeViews.ts
@@ -14,7 +14,7 @@ import { Disposable } from 'vs/base/common/lifecycle';
 import { ExtHostTreeViewsShape, MainThreadTreeViewsShape } from './extHost.protocol';
 import { ITreeItem, TreeViewItemHandleArg } from 'vs/workbench/common/views';
 import { ExtHostCommands, CommandsConverter } from 'vs/workbench/api/node/extHostCommands';
-import { asWinJsPromise } from 'vs/base/common/async';
+import { asThenable } from 'vs/base/common/async';
 import { TreeItemCollapsibleState, ThemeIcon } from 'vs/workbench/api/node/extHostTypes';
 import { isUndefinedOrNull } from 'vs/base/common/types';
 import { equals } from 'vs/base/common/arrays';
@@ -68,7 +68,7 @@ export class ExtHostTreeViews implements ExtHostTreeViewsShape {
 		};
 	}
 
-	$getChildren(treeViewId: string, treeItemHandle?: string): TPromise<ITreeItem[]> {
+	$getChildren(treeViewId: string, treeItemHandle?: string): Thenable<ITreeItem[]> {
 		const treeView = this.treeViews.get(treeViewId);
 		if (!treeView) {
 			return TPromise.wrapError<ITreeItem[]>(new Error(localize('treeView.notRegistered', 'No tree view with id \'{0}\' registered.', treeViewId)));
@@ -167,7 +167,7 @@ class ExtHostTreeView<T> extends Disposable {
 		}
 	}
 
-	getChildren(parentHandle?: TreeItemHandle): TPromise<ITreeItem[]> {
+	getChildren(parentHandle?: TreeItemHandle): Thenable<ITreeItem[]> {
 		const parentElement = parentHandle ? this.getExtensionElement(parentHandle) : void 0;
 		if (parentHandle && !parentElement) {
 			console.error(`No tree item with id \'${parentHandle}\' found.`);
@@ -222,7 +222,7 @@ class ExtHostTreeView<T> extends Disposable {
 		}
 	}
 
-	private resolveUnknownParentChain(element: T): TPromise<TreeNode[]> {
+	private resolveUnknownParentChain(element: T): Thenable<TreeNode[]> {
 		return this.resolveParent(element)
 			.then((parent) => {
 				if (!parent) {
@@ -237,16 +237,16 @@ class ExtHostTreeView<T> extends Disposable {
 			});
 	}
 
-	private resolveParent(element: T): TPromise<T> {
+	private resolveParent(element: T): Thenable<T> {
 		const node = this.nodes.get(element);
 		if (node) {
 			return TPromise.as(node.parent ? this.elements.get(node.parent.item.handle) : null);
 		}
-		return asWinJsPromise(() => this.dataProvider.getParent(element));
+		return asThenable(() => this.dataProvider.getParent(element));
 	}
 
-	private resolveTreeNode(element: T, parent?: TreeNode): TPromise<TreeNode> {
-		return asWinJsPromise(() => this.dataProvider.getTreeItem(element))
+	private resolveTreeNode(element: T, parent?: TreeNode): Thenable<TreeNode> {
+		return asThenable(() => this.dataProvider.getTreeItem(element))
 			.then(extTreeItem => this.createHandle(element, extTreeItem, parent, true))
 			.then(handle => this.getChildren(parent ? parent.item.handle : null)
 				.then(() => {
@@ -275,21 +275,21 @@ class ExtHostTreeView<T> extends Disposable {
 		return this.roots;
 	}
 
-	private fetchChildrenNodes(parentElement?: T): TPromise<TreeNode[]> {
+	private fetchChildrenNodes(parentElement?: T): Thenable<TreeNode[]> {
 		// clear children cache
 		this.clearChildren(parentElement);
 
 		const parentNode = parentElement ? this.nodes.get(parentElement) : void 0;
-		return asWinJsPromise(() => this.dataProvider.getChildren(parentElement))
+		return asThenable(() => this.dataProvider.getChildren(parentElement))
 			.then(elements => TPromise.join(
 				(elements || [])
 					.filter(element => !!element)
-					.map(element => asWinJsPromise(() => this.dataProvider.getTreeItem(element))
+					.map(element => asThenable(() => this.dataProvider.getTreeItem(element))
 						.then(extTreeItem => extTreeItem ? this.createAndRegisterTreeNode(element, extTreeItem, parentNode) : null))))
 			.then(nodes => nodes.filter(n => !!n));
 	}
 
-	private refresh(elements: T[]): TPromise<void> {
+	private refresh(elements: T[]): Thenable<void> {
 		const hasRoot = elements.some(element => !element);
 		if (hasRoot) {
 			this.clearAll(); // clear cache
@@ -345,11 +345,11 @@ class ExtHostTreeView<T> extends Disposable {
 			.then(() => Object.keys(itemsToRefresh).length ? this.proxy.$refresh(this.viewId, itemsToRefresh) : null);
 	}
 
-	private refreshNode(treeItemHandle: TreeItemHandle): TPromise<TreeNode> {
+	private refreshNode(treeItemHandle: TreeItemHandle): Thenable<TreeNode> {
 		const extElement = this.getExtensionElement(treeItemHandle);
 		const existing = this.nodes.get(extElement);
 		this.clearChildren(extElement); // clear children cache
-		return asWinJsPromise(() => this.dataProvider.getTreeItem(extElement))
+		return asThenable(() => this.dataProvider.getTreeItem(extElement))
 			.then(extTreeItem => {
 				if (extTreeItem) {
 					const newNode = this.createTreeNode(extElement, extTreeItem, existing.parent);
@@ -529,4 +529,4 @@ class ExtHostTreeView<T> extends Disposable {
 	dispose() {
 		this.clearAll();
 	}
-}
\ No newline at end of file
+}
diff --git a/src/vs/workbench/test/electron-browser/api/extHostTreeViews.test.ts b/src/vs/workbench/test/electron-browser/api/extHostTreeViews.test.ts
index a62fde4bcb8..e4b5a3f176a 100644
--- a/src/vs/workbench/test/electron-browser/api/extHostTreeViews.test.ts
+++ b/src/vs/workbench/test/electron-browser/api/extHostTreeViews.test.ts
@@ -538,7 +538,7 @@ suite('ExtHostTreeView', function () {
 			});
 	});
 
-	function loadCompleteTree(treeId, element?: string): TPromise<void> {
+	function loadCompleteTree(treeId, element?: string) {
 		return testObject.$getChildren(treeId, element)
 			.then(elements => elements.map(e => loadCompleteTree(treeId, e.handle)))
 			.then(() => null);
@@ -637,4 +637,4 @@ suite('ExtHostTreeView', function () {
 		constructor(readonly key: string) { }
 	}
 
-});
\ No newline at end of file
+});