diff --git a/src/vs/workbench/electron-browser/workbench.ts b/src/vs/workbench/electron-browser/workbench.ts
index a45547977950226bf143c0f93503953a5d3ae820..965c108967019fcaee195727d0f410668c29da50 100644
--- a/src/vs/workbench/electron-browser/workbench.ts
+++ b/src/vs/workbench/electron-browser/workbench.ts
@@ -883,7 +883,7 @@ export class Workbench implements IPartService {
 	}
 
 	public toggleMaximizedPanel(): void {
-		this.workbenchLayout.layout({ toggleMaximizedPanel: true });
+		this.workbenchLayout.layout({ toggleMaximizedPanel: true, source: Parts.PANEL_PART });
 	}
 
 	public isPanelMaximized(): boolean {