diff --git a/src/lib/models/event-groups/get-group-name.ts b/src/lib/models/event-groups/get-group-name.ts
index 8d38fde8c..33cdf42b9 100644
--- a/src/lib/models/event-groups/get-group-name.ts
+++ b/src/lib/models/event-groups/get-group-name.ts
@@ -113,7 +113,7 @@ export const getEventGroupLabel = (event: CommonHistoryEvent): string => {
 
 export const getEventGroupDisplayName = (
   event: CommonHistoryEvent,
-  initialEvent: CommonHistoryEvent,
+  initialEvent?: CommonHistoryEvent,
 ): string => {
   if (!event) return '';