diff --git a/course-matrix/frontend/src/pages/TimetableBuilder/Calendar.tsx b/course-matrix/frontend/src/pages/TimetableBuilder/Calendar.tsx
index a82e5244..20d70aec 100644
--- a/course-matrix/frontend/src/pages/TimetableBuilder/Calendar.tsx
+++ b/course-matrix/frontend/src/pages/TimetableBuilder/Calendar.tsx
@@ -236,7 +236,7 @@ const Calendar = React.memo<CalendarProps>(
         return;
       }
       // Create course events for the newly created timetable
-      const newTimetableId = data?.id;
+      const newTimetableId = data[0].id;
       for (const offeringId of newOfferingIds) {
         const { error: offeringError } = await createEvent({
           calendar_id: newTimetableId,
diff --git a/course-matrix/frontend/src/pages/TimetableBuilder/GeneratedCalendars.tsx b/course-matrix/frontend/src/pages/TimetableBuilder/GeneratedCalendars.tsx
index a55d87e4..0a66d153 100644
--- a/course-matrix/frontend/src/pages/TimetableBuilder/GeneratedCalendars.tsx
+++ b/course-matrix/frontend/src/pages/TimetableBuilder/GeneratedCalendars.tsx
@@ -133,7 +133,7 @@ export const GeneratedCalendars = React.memo<GeneratedCalendarsProps>(
         return;
       }
       // Create course events for the newly created timetable
-      const newTimetableId = data?.id;
+      const newTimetableId = data[0].id;
       for (const offering of currentTimetableOfferings) {
         const offeringId = offering.id;
         const { error: offeringError } = await createEvent({