diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index 347a59d1f50..ba90e871df0 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -2647,6 +2647,17 @@ declare namespace vscode {
 		 */
 		has(section: string): boolean;
 
+		/**
+		 * Update a configuration value. A value can be changed for the current
+		 * [workspace](#workspace.rootPath) only or globally for all instances of the
+		 * editor. The updated configuration values are persisted.
+		 *
+		 * @param section Configuration name, supports _dotted_ names.
+		 * @param value The new value.
+		 * @param global When `true` changes the configuration value for all instances of the editor.
+		 */
+		update(section: string, value: any, global: boolean): Thenable<void>;
+
 		/**
 		 * Readable dictionary that backs this configuration.
 		 * @readonly
diff --git a/src/vs/workbench/api/node/extHostConfiguration.ts b/src/vs/workbench/api/node/extHostConfiguration.ts
index 835ebf69510..760a4a7c9f7 100644
--- a/src/vs/workbench/api/node/extHostConfiguration.ts
+++ b/src/vs/workbench/api/node/extHostConfiguration.ts
@@ -9,7 +9,7 @@ import {illegalState} from 'vs/base/common/errors';
 import Event, {Emitter} from 'vs/base/common/event';
 import {WorkspaceConfiguration} from 'vscode';
 import {ExtHostConfigurationShape, MainThreadConfigurationShape} from './extHost.protocol';
-// import {ConfigurationTarget} from 'vs/workbench/services/configuration/common/configurationEditing';
+import {ConfigurationTarget} from 'vs/workbench/services/configuration/common/configurationEditing';
 
 export class ExtHostConfiguration extends ExtHostConfigurationShape {
 
@@ -52,11 +52,11 @@ export class ExtHostConfiguration extends ExtHostConfigurationShape {
 					result = defaultValue;
 				}
 				return result;
-			// },
-			// update: (key: string, value: any, global: boolean) => {
-			// 	key = section ? `${section}.${key}` : key;
-			// 	const target = global ? ConfigurationTarget.USER : ConfigurationTarget.WORKSPACE;
-			// 	return this._proxy.$updateConfigurationOption(target, key, value);
+			},
+			update: (key: string, value: any, global: boolean) => {
+				key = section ? `${section}.${key}` : key;
+				const target = global ? ConfigurationTarget.USER : ConfigurationTarget.WORKSPACE;
+				return this._proxy.$updateConfigurationOption(target, key, value);
 			}
 		};
 
diff --git a/src/vs/workbench/test/node/api/extHostConfiguration.test.ts b/src/vs/workbench/test/node/api/extHostConfiguration.test.ts
index 698c83097ab..f0dbfd633c3 100644
--- a/src/vs/workbench/test/node/api/extHostConfiguration.test.ts
+++ b/src/vs/workbench/test/node/api/extHostConfiguration.test.ts
@@ -9,7 +9,7 @@ import * as assert from 'assert';
 import {ExtHostConfiguration} from 'vs/workbench/api/node/extHostConfiguration';
 import {MainThreadConfigurationShape} from 'vs/workbench/api/node/extHost.protocol';
 import {TPromise} from 'vs/base/common/winjs.base';
-import {ConfigurationTarget/*, ConfigurationEditingErrorCode, IConfigurationEditingError*/} from 'vs/workbench/services/configuration/common/configurationEditing';
+import {ConfigurationTarget, ConfigurationEditingErrorCode, IConfigurationEditingError} from 'vs/workbench/services/configuration/common/configurationEditing';
 
 suite('ExtHostConfiguration', function () {
 
@@ -21,49 +21,49 @@ suite('ExtHostConfiguration', function () {
 		}
 	};
 
-	// function createExtHostConfiguration(data: any = {}, shape?: MainThreadConfigurationShape) {
-	// 	if (!shape) {
-	// 		shape = new class extends MainThreadConfigurationShape { };
-	// 	}
-	// 	const result = new ExtHostConfiguration(shape);
-	// 	result.$acceptConfigurationChanged(data);
-	// 	return result;
-	// }
+	function createExtHostConfiguration(data: any = {}, shape?: MainThreadConfigurationShape) {
+		if (!shape) {
+			shape = new class extends MainThreadConfigurationShape { };
+		}
+		const result = new ExtHostConfiguration(shape);
+		result.$acceptConfigurationChanged(data);
+		return result;
+	}
 
 	test('check illegal state', function () {
 		assert.throws(() => new ExtHostConfiguration(new class extends MainThreadConfigurationShape { }).getConfiguration('foo'));
 	});
 
-	// test('udate / section to key', function () {
+	test('udate / section to key', function () {
 
-	// 	const shape = new RecordingShape();
-	// 	const allConfig = createExtHostConfiguration({ foo: { bar: 1, far: 2 } }, shape);
+		const shape = new RecordingShape();
+		const allConfig = createExtHostConfiguration({ foo: { bar: 1, far: 2 } }, shape);
 
-	// 	let config = allConfig.getConfiguration('foo');
-	// 	config.update('bar', 42, true);
+		let config = allConfig.getConfiguration('foo');
+		config.update('bar', 42, true);
 
-	// 	assert.equal(shape.lastArgs[1], 'foo.bar');
-	// 	assert.equal(shape.lastArgs[2], 42);
+		assert.equal(shape.lastArgs[1], 'foo.bar');
+		assert.equal(shape.lastArgs[2], 42);
 
-	// 	config = allConfig.getConfiguration('');
-	// 	config.update('bar', 42, true);
-	// 	assert.equal(shape.lastArgs[1], 'bar');
+		config = allConfig.getConfiguration('');
+		config.update('bar', 42, true);
+		assert.equal(shape.lastArgs[1], 'bar');
 
-	// 	config.update('foo.bar', 42, true);
-	// 	assert.equal(shape.lastArgs[1], 'foo.bar');
-	// });
+		config.update('foo.bar', 42, true);
+		assert.equal(shape.lastArgs[1], 'foo.bar');
+	});
 
-	// test('update / error-state not OK', function () {
+	test('update / error-state not OK', function () {
 
-	// 	const shape = new class extends MainThreadConfigurationShape {
-	// 		$updateConfigurationOption(target: ConfigurationTarget, key: string, value: any): TPromise<any> {
-	// 			return TPromise.wrapError(<IConfigurationEditingError>{ code: ConfigurationEditingErrorCode.ERROR_UNKNOWN_KEY, message: 'Unknown Key' }); // something !== OK
-	// 		}
-	// 	};
+		const shape = new class extends MainThreadConfigurationShape {
+			$updateConfigurationOption(target: ConfigurationTarget, key: string, value: any): TPromise<any> {
+				return TPromise.wrapError(<IConfigurationEditingError>{ code: ConfigurationEditingErrorCode.ERROR_UNKNOWN_KEY, message: 'Unknown Key' }); // something !== OK
+			}
+		};
 
-	// 	return createExtHostConfiguration({}, shape)
-	// 		.getConfiguration('')
-	// 		.update('', true, false)
-	// 		.then(() => assert.ok(false), err => { /* expecting rejection */});
-	// });
+		return createExtHostConfiguration({}, shape)
+			.getConfiguration('')
+			.update('', true, false)
+			.then(() => assert.ok(false), err => { /* expecting rejection */});
+	});
 });