diff --git a/src/vs/platform/configuration/common/configuration.ts b/src/vs/platform/configuration/common/configuration.ts
index 94e02b37a29..8216a7805f0 100644
--- a/src/vs/platform/configuration/common/configuration.ts
+++ b/src/vs/platform/configuration/common/configuration.ts
@@ -9,6 +9,7 @@ import * as types from 'vs/base/common/types';
 import * as objects from 'vs/base/common/objects';
 import URI from 'vs/base/common/uri';
 import { StrictResourceMap } from 'vs/base/common/map';
+import { Workspace } from 'vs/platform/workspace/common/workspace';
 import { createDecorator } from 'vs/platform/instantiation/common/instantiation';
 import Event from 'vs/base/common/event';
 
@@ -199,16 +200,15 @@ export interface IConfigurationData<T> {
 	defaults: IConfiguraionModel<T>;
 	user: IConfiguraionModel<T>;
 	folders: { [folder: string]: IConfiguraionModel<T> };
-	workspaceUri: string;
 }
 
 export class Configuration<T> {
 
-	private _global: ConfigurationModel<T>;
-	private _workspace: ConfigurationModel<T>;
-	protected _foldersConsolidated: StrictResourceMap<ConfigurationModel<T>>;
+	private _globalConfiguration: ConfigurationModel<T>;
+	private _workspaceConfiguration: ConfigurationModel<T>;
+	protected _foldersConsolidatedConfigurations: StrictResourceMap<ConfigurationModel<T>>;
 
-	constructor(protected _defaults: ConfigurationModel<T>, protected _user: ConfigurationModel<T>, protected folders: StrictResourceMap<ConfigurationModel<T>> = new StrictResourceMap<ConfigurationModel<T>>(), protected workspaceUri?: URI) {
+	constructor(protected _defaults: ConfigurationModel<T>, protected _user: ConfigurationModel<T>, protected folders: StrictResourceMap<ConfigurationModel<T>> = new StrictResourceMap<ConfigurationModel<T>>(), protected _workspace?: Workspace) {
 		this.merge();
 	}
 
@@ -221,23 +221,23 @@ export class Configuration<T> {
 	}
 
 	get workspace(): ConfigurationModel<T> {
-		return this._workspace;
+		return this._workspaceConfiguration;
 	}
 
 	protected merge(): void {
-		this._global = this._workspace = new ConfigurationModel<T>().merge(this._defaults).merge(this._user);
-		this._foldersConsolidated = new StrictResourceMap<ConfigurationModel<T>>();
+		this._globalConfiguration = this._workspaceConfiguration = new ConfigurationModel<T>().merge(this._defaults).merge(this._user);
+		this._foldersConsolidatedConfigurations = new StrictResourceMap<ConfigurationModel<T>>();
 		for (const folder of this.folders.keys()) {
 			this.mergeFolder(folder);
 		}
 	}
 
 	protected mergeFolder(folder: URI) {
-		if (this.workspaceUri && this.workspaceUri.fsPath === folder.fsPath) {
-			this._workspace = new ConfigurationModel<T>().merge(this._global).merge(this.folders.get(this.workspaceUri));
-			this._foldersConsolidated.set(folder, this._workspace);
+		if (this._workspace && this.workspaceUri.fsPath === folder.fsPath) {
+			this._workspaceConfiguration = new ConfigurationModel<T>().merge(this._globalConfiguration).merge(this.folders.get(this.workspaceUri));
+			this._foldersConsolidatedConfigurations.set(folder, this._workspaceConfiguration);
 		} else {
-			this._foldersConsolidated.set(folder, new ConfigurationModel<T>().merge(this._workspace).merge(this.folders.get(folder)));
+			this._foldersConsolidatedConfigurations.set(folder, new ConfigurationModel<T>().merge(this._workspaceConfiguration).merge(this.folders.get(folder)));
 		}
 	}
 
@@ -251,8 +251,8 @@ export class Configuration<T> {
 		return {
 			default: objects.clone(getConfigurationValue<C>(overrideIdentifier ? this._defaults.override(overrideIdentifier).contents : this._defaults.contents, key)),
 			user: objects.clone(getConfigurationValue<C>(overrideIdentifier ? this._user.override(overrideIdentifier).contents : this._user.contents, key)),
-			workspace: objects.clone(this.workspaceUri ? getConfigurationValue<C>(overrideIdentifier ? this.folders.get(this.workspaceUri).override(overrideIdentifier).contents : this.folders.get(this.workspaceUri).contents, key) : void 0),
-			value: objects.clone(getConfigurationValue<C>(overrideIdentifier ? this._workspace.override(overrideIdentifier).contents : this._workspace.contents, key))
+			workspace: objects.clone(this._workspace ? getConfigurationValue<C>(overrideIdentifier ? this.folders.get(this.workspaceUri).override(overrideIdentifier).contents : this.folders.get(this.workspaceUri).contents, key) : void 0),
+			value: objects.clone(getConfigurationValue<C>(overrideIdentifier ? this._workspaceConfiguration.override(overrideIdentifier).contents : this._workspaceConfiguration.contents, key))
 		};
 	}
 
@@ -260,7 +260,7 @@ export class Configuration<T> {
 		return {
 			default: this._defaults.keys,
 			user: this._user.keys,
-			workspace: this.workspaceUri ? this.folders.get(this.workspaceUri).keys : []
+			workspace: this._workspace ? this.folders.get(this.workspaceUri).keys : []
 		};
 	}
 
@@ -296,8 +296,12 @@ export class Configuration<T> {
 		return result;
 	}
 
+	protected get workspaceUri(): URI {
+		return this.workspace ? this._workspace.roots[0] : null;
+	}
+
 	private getConfigurationModel<C>(overrides: IConfigurationOverrides): ConfigurationModel<any> {
-		let configurationModel = overrides.resource ? this._foldersConsolidated.get(overrides.resource) || this._workspace : this._workspace;
+		let configurationModel = overrides.resource ? this._foldersConsolidatedConfigurations.get(overrides.resource) || this._workspaceConfiguration : this._workspaceConfiguration;
 		return overrides.language ? configurationModel.override<T>(overrides.language) : configurationModel;
 	}
 
@@ -315,20 +319,18 @@ export class Configuration<T> {
 				const { contents, overrides } = this.folders.get(folder);
 				result[folder.toString()] = { contents, overrides };
 				return result;
-			}, Object.create({})),
-			workspaceUri: this.workspaceUri ? this.workspaceUri.toString() : void 0
+			}, Object.create({}))
 		};
 	}
 
-	public static parse(data: IConfigurationData<any>): Configuration<any> {
+	public static parse(data: IConfigurationData<any>, workspace: Workspace): Configuration<any> {
 		const defaults = Configuration.parseConfigurationModel(data.defaults);
 		const user = Configuration.parseConfigurationModel(data.user);
 		const folders: StrictResourceMap<ConfigurationModel<any>> = Object.keys(data.folders).reduce((result, key) => {
 			result.set(URI.parse(key), Configuration.parseConfigurationModel(data.folders[key]));
 			return result;
 		}, new StrictResourceMap<ConfigurationModel<any>>());
-		const workspaceUri = data.workspaceUri ? URI.parse(data.workspaceUri) : void 0;
-		return new Configuration<any>(defaults, user, folders, workspaceUri);
+		return new Configuration<any>(defaults, user, folders, workspace);
 	}
 
 	private static parseConfigurationModel(model: IConfiguraionModel<any>): ConfigurationModel<any> {
diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index 4b1429aa294..7c4e72c853d 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -83,7 +83,8 @@ export function createApiFactory(
 	const extHostEditors = col.define(ExtHostContext.ExtHostEditors).set<ExtHostEditors>(new ExtHostEditors(threadService, extHostDocumentsAndEditors));
 	const extHostCommands = col.define(ExtHostContext.ExtHostCommands).set<ExtHostCommands>(new ExtHostCommands(threadService, extHostHeapService));
 	const extHostTreeViews = col.define(ExtHostContext.ExtHostTreeViews).set<ExtHostTreeViews>(new ExtHostTreeViews(threadService, extHostCommands));
-	const extHostConfiguration = col.define(ExtHostContext.ExtHostConfiguration).set<ExtHostConfiguration>(new ExtHostConfiguration(threadService.get(MainContext.MainThreadConfiguration), initData.configuration));
+	const extHostWorkspace = col.define(ExtHostContext.ExtHostWorkspace).set<ExtHostWorkspace>(new ExtHostWorkspace(threadService, initData.workspace));
+	const extHostConfiguration = col.define(ExtHostContext.ExtHostConfiguration).set<ExtHostConfiguration>(new ExtHostConfiguration(threadService.get(MainContext.MainThreadConfiguration), initData.configuration, extHostWorkspace));
 	const extHostDiagnostics = col.define(ExtHostContext.ExtHostDiagnostics).set<ExtHostDiagnostics>(new ExtHostDiagnostics(threadService));
 	const languageFeatures = col.define(ExtHostContext.ExtHostLanguageFeatures).set<ExtHostLanguageFeatures>(new ExtHostLanguageFeatures(threadService, extHostDocuments, extHostCommands, extHostHeapService, extHostDiagnostics));
 	const extHostFileSystemEvent = col.define(ExtHostContext.ExtHostFileSystemEventService).set<ExtHostFileSystemEventService>(new ExtHostFileSystemEventService());
@@ -91,7 +92,6 @@ export function createApiFactory(
 	const extHostTerminalService = col.define(ExtHostContext.ExtHostTerminalService).set<ExtHostTerminalService>(new ExtHostTerminalService(threadService));
 	const extHostSCM = col.define(ExtHostContext.ExtHostSCM).set<ExtHostSCM>(new ExtHostSCM(threadService, extHostCommands));
 	const extHostTask = col.define(ExtHostContext.ExtHostTask).set<ExtHostTask>(new ExtHostTask(threadService));
-	const extHostWorkspace = col.define(ExtHostContext.ExtHostWorkspace).set<ExtHostWorkspace>(new ExtHostWorkspace(threadService, initData.workspace));
 	col.define(ExtHostContext.ExtHostExtensionService).set(extensionService);
 	col.finish(false, threadService);
 
diff --git a/src/vs/workbench/api/node/extHostConfiguration.ts b/src/vs/workbench/api/node/extHostConfiguration.ts
index 5ee24322929..da84ebf96ba 100644
--- a/src/vs/workbench/api/node/extHostConfiguration.ts
+++ b/src/vs/workbench/api/node/extHostConfiguration.ts
@@ -7,6 +7,7 @@
 import { mixin } from 'vs/base/common/objects';
 import Event, { Emitter } from 'vs/base/common/event';
 import { WorkspaceConfiguration } from 'vscode';
+import { ExtHostWorkspace } from 'vs/workbench/api/node/extHostWorkspace';
 import { ExtHostConfigurationShape, MainThreadConfigurationShape } from './extHost.protocol';
 import { IConfigurationData, Configuration } from 'vs/platform/configuration/common/configuration';
 import { ConfigurationTarget } from 'vs/workbench/services/configuration/common/configurationEditing';
@@ -29,7 +30,7 @@ export class ExtHostConfiguration extends ExtHostConfigurationShape {
 	private _data: IConfigurationData<any>;
 	private _configuration: Configuration<any>;
 
-	constructor(proxy: MainThreadConfigurationShape, data: IConfigurationData<any>) {
+	constructor(proxy: MainThreadConfigurationShape, data: IConfigurationData<any>, private extWorkspace: ExtHostWorkspace) {
 		super();
 		this._proxy = proxy;
 		this._data = data;
@@ -47,7 +48,7 @@ export class ExtHostConfiguration extends ExtHostConfigurationShape {
 
 	private get configuration(): Configuration<any> {
 		if (!this._configuration) {
-			this._configuration = Configuration.parse(this._data);
+			this._configuration = Configuration.parse(this._data, this.extWorkspace.workspace);
 		}
 		return this._configuration;
 	}
diff --git a/src/vs/workbench/api/node/extHostWorkspace.ts b/src/vs/workbench/api/node/extHostWorkspace.ts
index e222fb03816..8cb2947fe41 100644
--- a/src/vs/workbench/api/node/extHostWorkspace.ts
+++ b/src/vs/workbench/api/node/extHostWorkspace.ts
@@ -9,6 +9,7 @@ import Event, { Emitter } from 'vs/base/common/event';
 import { normalize } from 'vs/base/common/paths';
 import { isFalsyOrEmpty } from 'vs/base/common/arrays';
 import { relative } from 'path';
+import { Workspace } from 'vs/platform/workspace/common/workspace';
 import { IThreadService } from 'vs/workbench/services/thread/common/threadService';
 import { IResourceEdit } from 'vs/editor/common/services/bulkEdit';
 import { TPromise } from 'vs/base/common/winjs.base';
@@ -22,18 +23,22 @@ export class ExtHostWorkspace extends ExtHostWorkspaceShape {
 
 	private readonly _onDidChangeWorkspace = new Emitter<this>();
 	private readonly _proxy: MainThreadWorkspaceShape;
-	private _workspace: IWorkspaceData;
+	private _workspace: Workspace;
 
 	readonly onDidChangeWorkspace: Event<this> = this._onDidChangeWorkspace.event;
 
-	constructor(threadService: IThreadService, workspace: IWorkspaceData) {
+	constructor(threadService: IThreadService, data: IWorkspaceData) {
 		super();
 		this._proxy = threadService.get(MainContext.MainThreadWorkspace);
-		this._workspace = workspace;
+		this._workspace = data ? new Workspace(data.id, data.name, data.roots) : null;
 	}
 
 	// --- workspace ---
 
+	get workspace(): Workspace {
+		return this._workspace;
+	}
+
 	getPath(): string {
 		// this is legacy from the days before having
 		// multi-root and we keep it only alive if there
@@ -69,8 +74,8 @@ export class ExtHostWorkspace extends ExtHostWorkspaceShape {
 		return normalize(path);
 	}
 
-	$acceptWorkspaceData(workspace: IWorkspaceData): void {
-		this._workspace = workspace;
+	$acceptWorkspaceData(data: IWorkspaceData): void {
+		this._workspace = data ? new Workspace(data.id, data.name, data.roots) : null;
 		this._onDidChangeWorkspace.fire(this);
 	}
 
diff --git a/src/vs/workbench/services/configuration/node/configuration.ts b/src/vs/workbench/services/configuration/node/configuration.ts
index cd6fa13bedc..28a61bbc46c 100644
--- a/src/vs/workbench/services/configuration/node/configuration.ts
+++ b/src/vs/workbench/services/configuration/node/configuration.ts
@@ -69,7 +69,11 @@ export class WorkspaceConfigurationService extends Disposable implements IWorksp
 	constructor(private environmentService: IEnvironmentService, private readonly legacyWorkspace?: LegacyWorkspace, private workspaceSettingsRootFolder: string = WORKSPACE_CONFIG_FOLDER_DEFAULT_NAME) {
 		super();
 
-		this.workspace = legacyWorkspace ? new Workspace(createHash('md5').update(legacyWorkspace.resource.fsPath).update(legacyWorkspace.ctime ? String(legacyWorkspace.ctime) : '').digest('hex'), basename(legacyWorkspace.resource.fsPath), [legacyWorkspace.resource]) : null;
+		this.workspace = legacyWorkspace ? new Workspace(
+			createHash('md5').update(legacyWorkspace.resource.fsPath).update(legacyWorkspace.ctime ? String(legacyWorkspace.ctime) : '').digest('hex'),
+			basename(legacyWorkspace.resource.fsPath),
+			[legacyWorkspace.resource]
+		) : null;
 		this._register(this.onDidUpdateConfiguration(e => this.resolveAdditionalFolders(true)));
 
 		this.baseConfigurationService = this._register(new GlobalConfigurationService(environmentService));
@@ -233,7 +237,7 @@ export class WorkspaceConfigurationService extends Disposable implements IWorksp
 
 	private initCaches(): void {
 		this.cachedFolderConfigs = new StrictResourceMap<FolderConfiguration<any>>();
-		this._configuration = new Configuration(<any>this.baseConfigurationService.configuration(), new StrictResourceMap<FolderConfigurationModel<any>>(), this.workspaceUri);
+		this._configuration = new Configuration(<any>this.baseConfigurationService.configuration(), new StrictResourceMap<FolderConfigurationModel<any>>(), this.workspace);
 		this.initCachesForFolders(this.workspace ? this.workspace.roots : []);
 	}
 
@@ -467,12 +471,12 @@ function resolveStat(resource: URI): TPromise<IStat> {
 
 class Configuration<T> extends BaseConfiguration<T> {
 
-	constructor(private _baseConfiguration: Configuration<T>, protected folders: StrictResourceMap<FolderConfigurationModel<T>>, workspaceUri: URI) {
-		super(_baseConfiguration.defaults, _baseConfiguration.user, folders, workspaceUri);
+	constructor(private _baseConfiguration: Configuration<T>, protected folders: StrictResourceMap<FolderConfigurationModel<T>>, workspace: Workspace) {
+		super(_baseConfiguration.defaults, _baseConfiguration.user, folders, workspace);
 	}
 
 	updateBaseConfiguration(baseConfiguration: Configuration<T>): boolean {
-		const current = new Configuration(this._baseConfiguration, this.folders, this.workspaceUri);
+		const current = new Configuration(this._baseConfiguration, this.folders, this._workspace);
 
 		this._defaults = baseConfiguration.defaults;
 		this._user = baseConfiguration.user;
@@ -489,13 +493,13 @@ class Configuration<T> extends BaseConfiguration<T> {
 	}
 
 	deleteFolderConfiguration(folder: URI): boolean {
-		if (this.workspaceUri && this.workspaceUri.fsPath === folder.fsPath) {
+		if (this.workspace && this.workspaceUri.fsPath === folder.fsPath) {
 			// Do not remove workspace configuration
 			return false;
 		}
 
 		this.folders.delete(folder);
-		return this._foldersConsolidated.delete(folder);
+		return this._foldersConsolidatedConfigurations.delete(folder);
 	}
 
 	getFolderConfigurationModel(folder: URI): FolderConfigurationModel<T> {
@@ -511,11 +515,11 @@ class Configuration<T> extends BaseConfiguration<T> {
 			return false;
 		}
 
-		if (this._foldersConsolidated.size !== other._foldersConsolidated.size) {
+		if (this._foldersConsolidatedConfigurations.size !== other._foldersConsolidatedConfigurations.size) {
 			return false;
 		}
 
-		for (const resource of this._foldersConsolidated.keys()) {
+		for (const resource of this._foldersConsolidatedConfigurations.keys()) {
 			if (!objects.equals(this.getValue(null, { resource }), other.getValue(null, { resource }))) {
 				return false;
 			}
diff --git a/src/vs/workbench/test/electron-browser/api/extHostConfiguration.test.ts b/src/vs/workbench/test/electron-browser/api/extHostConfiguration.test.ts
index acdf7e0de9f..a07b32c76b4 100644
--- a/src/vs/workbench/test/electron-browser/api/extHostConfiguration.test.ts
+++ b/src/vs/workbench/test/electron-browser/api/extHostConfiguration.test.ts
@@ -6,11 +6,13 @@
 'use strict';
 
 import * as assert from 'assert';
+import { ExtHostWorkspace } from 'vs/workbench/api/node/extHostWorkspace';
 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 { ConfigurationModel } from 'vs/platform/configuration/common/configuration';
+import { TestThreadService } from './testThreadService';
 
 suite('ExtHostConfiguration', function () {
 
@@ -29,9 +31,8 @@ suite('ExtHostConfiguration', function () {
 		return new ExtHostConfiguration(shape, {
 			defaults: new ConfigurationModel(contents),
 			user: new ConfigurationModel(contents),
-			folders: Object.create(null),
-			workspaceUri: void 0
-		});
+			folders: Object.create(null)
+		}, new ExtHostWorkspace(new TestThreadService(), null));
 	}
 
 	test('getConfiguration fails regression test 1.7.1 -> 1.8 #15552', function () {