diff --git a/src/lib/checkbox/checkbox.spec.ts b/src/lib/checkbox/checkbox.spec.ts
index 9c0d81a7dd0..3cfd978c364 100644
--- a/src/lib/checkbox/checkbox.spec.ts
+++ b/src/lib/checkbox/checkbox.spec.ts
@@ -810,7 +810,6 @@ class SingleCheckbox {
   disableRipple: boolean = false;
   parentElementClicked: boolean = false;
   parentElementKeyedUp: boolean = false;
-  lastKeydownEvent: Event = null;
   checkboxColor: string = 'primary';
   checkboxValue: string = 'single_checkbox';