diff --git a/src/tsconfig.base.json b/src/tsconfig.base.json
index b782f00466a..907c210b530 100644
--- a/src/tsconfig.base.json
+++ b/src/tsconfig.base.json
@@ -3,7 +3,6 @@
 		"module": "amd",
 		"moduleResolution": "node",
 		"noImplicitAny": true,
-		"target": "es5",
 		"experimentalDecorators": true,
 		"noImplicitReturns": true,
 		"noUnusedLocals": true,
diff --git a/src/vs/base/parts/tree/browser/treeModel.ts b/src/vs/base/parts/tree/browser/treeModel.ts
index 3542756834c..ba1b0d77836 100644
--- a/src/vs/base/parts/tree/browser/treeModel.ts
+++ b/src/vs/base/parts/tree/browser/treeModel.ts
@@ -5,7 +5,7 @@
 
 import * as Assert from 'vs/base/common/assert';
 import { onUnexpectedError } from 'vs/base/common/errors';
-import { IDisposable, combinedDisposable } from 'vs/base/common/lifecycle';
+import { IDisposable, combinedDisposable, Disposable } from 'vs/base/common/lifecycle';
 import { INavigator } from 'vs/base/common/iterator';
 import * as _ from './tree';
 import { Event, Emitter, EventMultiplexer, Relay } from 'vs/base/common/event';
@@ -865,7 +865,7 @@ export class TreeModel {
 	private lock!: Lock;
 	private input: Item | null;
 	private registry: ItemRegistry = new ItemRegistry();
-	private registryDisposable!: IDisposable;
+	private registryDisposable: IDisposable = Disposable.None;
 	private traitsToItems: ITraitMap;
 
 	private _onSetInput = new Emitter<IInputEvent>();
diff --git a/test/smoke/tsconfig.json b/test/smoke/tsconfig.json
index 1b0b03c2d67..6f0b40e93e5 100644
--- a/test/smoke/tsconfig.json
+++ b/test/smoke/tsconfig.json
@@ -4,7 +4,7 @@
 		"noImplicitAny": false,
 		"removeComments": false,
 		"preserveConstEnums": true,
-		"target": "es2016",
+		"target": "es2017",
 		"strictNullChecks": true,
 		"noUnusedParameters": false,
 		"noUnusedLocals": true,
@@ -18,4 +18,4 @@
 	"exclude": [
 		"node_modules"
 	]
-}
\ No newline at end of file
+}