diff --git a/CHANGELOG.md b/CHANGELOG.md
index a6be6ef51..04f7b1390 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,8 @@
 ## Next release
 
 - improvement: add idp_slo_service_url(logout requests url) to saml provider
+- Fix a bug: event canceled places error
+- [TODO DEPLOY] `rails fablab:setup:build_places_cache`
 
 ## v6.3.13 2024 February 19
 
diff --git a/app/models/slots_reservation.rb b/app/models/slots_reservation.rb
index f81ef4c59..9fb35d500 100644
--- a/app/models/slots_reservation.rb
+++ b/app/models/slots_reservation.rb
@@ -66,10 +66,13 @@ def remove_from_places_cache(target_slot = slot)
   # @param target_slot [Slot]
   def update_places_cache(operation, target_slot = slot)
     if reservation.reservable_type == 'Event'
+      total_booked_seats = reservation.nb_reserve_places
+      total_booked_seats += reservation.tickets.map(&:booked).map(&:to_i).reduce(:+) if reservation.tickets.count.positive?
+      total_booked_seats = 0 if reservation.reservable.pre_registration
       Slots::PlacesCacheService.change_places(target_slot,
                                               reservation.reservable_type,
                                               reservation.reservable_id,
-                                              reservation.reservable.pre_registration ? 0 : reservation.total_booked_seats,
+                                              total_booked_seats,
                                               operation)
     else
       Slots::PlacesCacheService.change_places(target_slot, reservation.reservable_type, reservation.reservable_id, 1, operation)