diff --git a/src/utilities/popover.ts b/src/utilities/popover.ts
index 3bbf71b0f..a64689046 100644
--- a/src/utilities/popover.ts
+++ b/src/utilities/popover.ts
@@ -160,5 +160,5 @@ export interface PopoverOptions {
   visibleClass?: string;
   onAfterShow?: () => any;
   onAfterHide?: () => any;
-  onTransitionEnd?: () => any;
+  onTransitionEnd?: (event: TransitionEvent) => any;
 }