diff --git a/program/services.py b/program/services.py
index 295a8458a3808c8e2b74b114e0ac7673e0dbfdc4..1aeb018b43f4efcab6ce9379ff1048f046ed4f43 100644
--- a/program/services.py
+++ b/program/services.py
@@ -416,8 +416,7 @@ def make_conflicts(sdl, schedule_pk, show_pk):
     return conflicts
 
 
-# TODO: add type annotations
-def generate_timeslots(schedule):
+def generate_timeslots(schedule: Schedule) -> list[TimeSlot]:
     """
     Returns a list of timeslot objects based on a schedule and its rrule
     Returns past timeslots as well, starting from first_date (not today)