diff --git a/packages/property-inspector/src/index.ts b/packages/property-inspector/src/index.ts
index 1ad50da33100..002f54d82f0e 100644
--- a/packages/property-inspector/src/index.ts
+++ b/packages/property-inspector/src/index.ts
@@ -110,10 +110,12 @@ abstract class PropertyInspectorProvider extends Widget
         this._inspectors.delete(owner);
         break;
       case 'showPanel':
-        if (current == owner) {
+        if (current === owner) {
           this.showPanel();
         }
         break;
+      default:
+        throw new Error('Unsupported inspector action');
     }
   }