diff --git a/src/vs/workbench/browser/parts/panel/panelPart.ts b/src/vs/workbench/browser/parts/panel/panelPart.ts
index fa06f0b790717872e0a7de39af679fd6cd7dd113..0657833549958c71fa7b390f57b46e3588cec951 100644
--- a/src/vs/workbench/browser/parts/panel/panelPart.ts
+++ b/src/vs/workbench/browser/parts/panel/panelPart.ts
@@ -137,7 +137,7 @@ export class PanelPart extends CompositePart<Panel> implements IPanelService {
 		const id = viewlet.getId();
 
 		if (this.activePanelContextKey.get() === id) {
-			this.activePanelContextKey.set('');
+			this.activePanelContextKey.reset();
 		}
 	}
 
@@ -301,6 +301,7 @@ export class PanelPart extends CompositePart<Panel> implements IPanelService {
 	}
 
 	dispose(): void {
+		super.dispose();
 		this.disposables = dispose(this.disposables);
 	}
 }
diff --git a/src/vs/workbench/services/viewlet/browser/viewletService.ts b/src/vs/workbench/services/viewlet/browser/viewletService.ts
index 6b3d31eaaff06a73a77f202e16af23f2a06d8392..0a6b990f23fa8d04833e644969c1450e2d2fb4aa 100644
--- a/src/vs/workbench/services/viewlet/browser/viewletService.ts
+++ b/src/vs/workbench/services/viewlet/browser/viewletService.ts
@@ -57,7 +57,7 @@ export class ViewletService implements IViewletService {
 		const id = viewlet.getId();
 
 		if (this.activeViewletContextKey.get() === id) {
-			this.activeViewletContextKey.set('');
+			this.activeViewletContextKey.reset();
 		}
 	}