diff --git a/openapi/components/schemas/CalendarEvent.yaml b/openapi/components/schemas/CalendarEvent.yaml
index 88b32530..81147ca3 100644
--- a/openapi/components/schemas/CalendarEvent.yaml
+++ b/openapi/components/schemas/CalendarEvent.yaml
@@ -19,6 +19,7 @@ properties:
     type: string
   durationInMs:
     type: integer
+    format: int64
   endsAt:
     type: string
     format: date-time