diff --git a/packages/core/CalendarManager.ts b/packages/core/CalendarManager.ts
index 379fd20bd0..cf33d669cf 100644
--- a/packages/core/CalendarManager.ts
+++ b/packages/core/CalendarManager.ts
@@ -267,9 +267,9 @@ export const updateEvent = async (
       : undefined;
 
   if (Array.isArray(updatedResult)) {
-    calWarnings = updatedResult.flatMap((res) => res.additionalInfo.calWarnings ?? []);
+    calWarnings = updatedResult.flatMap((res) => res.additionalInfo?.calWarnings ?? []);
   } else {
-    calWarnings = updatedResult?.additionalInfo.calWarnings;
+    calWarnings = updatedResult?.additionalInfo?.calWarnings || [];
   }
 
   return {