diff --git a/src/vs/workbench/browser/layout.ts b/src/vs/workbench/browser/layout.ts
index 9978171ad5e235d24ca3232efa7b8b51139b50f0..13c618ca344e5fe64f91830b0107efbb652a1087 100644
--- a/src/vs/workbench/browser/layout.ts
+++ b/src/vs/workbench/browser/layout.ts
@@ -43,8 +43,6 @@ interface PartLayoutInfo {
 	statusbar: { height: number; };
 }
 
-interface ILayoutInternalOptions extends ILayoutOptions { };
-
 /**
  * The workbench layout is responsible to lay out all parts that make the Workbench.
  */
diff --git a/src/vs/workbench/services/part/common/partService.ts b/src/vs/workbench/services/part/common/partService.ts
index 4e6cb6266a684a7bfda534a8331fa3035c48fcf4..38274b7d4ca3dbec22ae8c0c8433b56293c5cf5a 100644
--- a/src/vs/workbench/services/part/common/partService.ts
+++ b/src/vs/workbench/services/part/common/partService.ts
@@ -25,7 +25,7 @@ export enum Position {
 
 export interface ILayoutOptions {
 	toggleMaximizedPanel?: boolean;
-	source: Parts;
+	source?: Parts;
 }
 
 export const IPartService = createDecorator<IPartService>('partService');