diff --git a/src/vs/workbench/api/node/extHostWorkspace.ts b/src/vs/workbench/api/node/extHostWorkspace.ts
index c56bf79591b..7ec394f6913 100644
--- a/src/vs/workbench/api/node/extHostWorkspace.ts
+++ b/src/vs/workbench/api/node/extHostWorkspace.ts
@@ -19,19 +19,19 @@ export class ExtHostWorkspace extends ExtHostWorkspaceShape {
 
 	private static _requestIdPool = 0;
 
-	private _proxy: MainThreadWorkspaceShape;
-	private _workspacePath: string;
+	private readonly _proxy: MainThreadWorkspaceShape;
+	private _workspaceFolders: URI[];
 
 	constructor(threadService: IThreadService, folders: URI[]) {
 		super();
 		this._proxy = threadService.get(MainContext.MainThreadWorkspace);
-		this._workspacePath = isFalsyOrEmpty(folders) ? undefined : folders[0].fsPath;
+		this._workspaceFolders = folders;
 	}
 
 	// --- workspace ---
 
 	getPath(): string {
-		return this._workspacePath;
+		return isFalsyOrEmpty(this._workspaceFolders) ? undefined : this._workspaceFolders[0].fsPath;
 	}
 
 	getRelativePath(pathOrUri: string | vscode.Uri): string {
@@ -47,20 +47,24 @@ export class ExtHostWorkspace extends ExtHostWorkspaceShape {
 			return path;
 		}
 
-		if (!this._workspacePath) {
+		if (isFalsyOrEmpty(this._workspaceFolders)) {
 			return normalize(path);
 		}
 
-		let result = relative(this._workspacePath, path);
-		if (!result || result.indexOf('..') === 0) {
-			return normalize(path);
+		for (const { fsPath } of this._workspaceFolders) {
+			let result = relative(fsPath, path);
+			if (!result || result.indexOf('..') === 0) {
+				continue;
+			}
+			return normalize(result);
 		}
 
-		return normalize(result);
+		return normalize(path);
 	}
 
-	$acceptWorkspaceData(folders: URI[]): void {
-		// todo@joh do something, align with ctor URI[] vs IWorkspace
+	$acceptWorkspaceData(workspaceFolders: URI[]): void {
+		//TODO@joh equality-check, emit event etc.
+		this._workspaceFolders = workspaceFolders;
 	}
 
 	// --- search ---
diff --git a/src/vs/workbench/test/electron-browser/api/extHostWorkspace.test.ts b/src/vs/workbench/test/electron-browser/api/extHostWorkspace.test.ts
index 413e9f14fb2..36430d52357 100644
--- a/src/vs/workbench/test/electron-browser/api/extHostWorkspace.test.ts
+++ b/src/vs/workbench/test/electron-browser/api/extHostWorkspace.test.ts
@@ -22,6 +22,7 @@ suite('ExtHostWorkspace', function () {
 
 		assert.equal(ws.getRelativePath(''), '');
 		assert.equal(ws.getRelativePath('/foo/bar'), '/foo/bar');
+		assert.equal(ws.getRelativePath('in/out'), 'in/out');
 	});
 
 	test('asRelativePath, same paths, #11402', function () {
@@ -33,6 +34,18 @@ suite('ExtHostWorkspace', function () {
 
 		const input2 = '/home/aeschli/workspaces/samples/docker/a.file';
 		assert.equal(ws.getRelativePath(input2), 'a.file');
+	});
 
+	test('asRelativePath, no workspace', function () {
+		const ws = new ExtHostWorkspace(new TestThreadService(), null);
+		assert.equal(ws.getRelativePath(''), '');
+		assert.equal(ws.getRelativePath('/foo/bar'), '/foo/bar');
+	});
+
+	test('asRelativePath, multiple folders', function () {
+		const ws = new ExtHostWorkspace(new TestThreadService(), [URI.file('/Coding/One'), URI.file('/Coding/Two')]);
+		assert.equal(ws.getRelativePath('/Coding/One/file.txt'), 'file.txt');
+		assert.equal(ws.getRelativePath('/Coding/Two/files/out.txt'), 'files/out.txt');
+		assert.equal(ws.getRelativePath('/Coding/Two2/files/out.txt'), '/Coding/Two2/files/out.txt');
 	});
 });