diff --git a/chrono/api/views.py b/chrono/api/views.py
index 7ae8a818..2c253fb6 100644
--- a/chrono/api/views.py
+++ b/chrono/api/views.py
@@ -265,7 +265,7 @@ def get_all_slots(
         )
         booked_events = (
             Event.objects.filter(
-                agenda__in=agenda_ids,
+                agenda__in=agendas,
                 start_datetime__gte=used_min_datetime - max_meeting_duration_td,
                 start_datetime__lte=used_max_datetime,
                 booking__user_external_id=user_external_id,
@@ -278,7 +278,10 @@ def get_all_slots(
         # compute exclusion set by desk from all bookings, using
         # itertools.groupby() to group them by desk_id
         user_bookings = IntervalSet.from_ordered(
-            (event_start_datetime, event_start_datetime + datetime.timedelta(minutes=event_duration))
+            (
+                event_start_datetime,
+                event_start_datetime + datetime.timedelta(minutes=event_duration),
+            )
             for event_start_datetime, event_duration in booked_events
         )
 
diff --git a/tests/api/fillslot/test_all.py b/tests/api/fillslot/test_all.py
index b16a9eb4..d816b6cb 100644
--- a/tests/api/fillslot/test_all.py
+++ b/tests/api/fillslot/test_all.py
@@ -2550,3 +2550,70 @@ def test_fillslot_recurring_event_booking_forbidden(app, user):
     resp = app.post('/api/agenda/%s/fillslot/%s/' % (agenda.slug, event.slug))
     assert resp.json['err'] == 1
     assert resp.json['err_class'] == 'event is recurrent'
+
+
+# monday 15th march at 12:00 CEST
+@pytest.mark.freeze_time('2021-03-15T12:00:00+01:00')
+def test_user_external_id(app, user):
+    user_external_id = 'foobar'
+    meeting_agenda_1 = Agenda.objects.create(
+        label='Meeting agenda', slug='mt1', kind='meetings', minimal_booking_delay=0
+    )
+    desk = Desk.objects.create(agenda=meeting_agenda_1, slug='desk')
+    meeting_type = MeetingType.objects.create(agenda=meeting_agenda_1, slug='mtt')
+    TimePeriod.objects.create(
+        weekday=0, start_time=datetime.time(9, 0), end_time=datetime.time(17, 00), desk=desk
+    )
+    meeting_agenda_2 = meeting_agenda_1.duplicate()
+    meeting_agenda_2.maximal_booking_delay = 20
+    meeting_agenda_2.save()
+    meeting_agenda_3 = meeting_agenda_1.duplicate()
+    meeting_agenda_3.maximal_booking_delay = 30
+    meeting_agenda_3.save()
+
+    virtual_agenda = Agenda.objects.create(label='Virtual Agenda', kind='virtual')
+    virtual_agenda.real_agendas.add(meeting_agenda_1, meeting_agenda_2, meeting_agenda_3)
+
+    meeting_agenda_1_datetimes_url = f'/api/agenda/{meeting_agenda_1.slug}/meetings/{meeting_type.slug}/datetimes/?user_external_id={user_external_id}'
+    meeting_agenda_2_datetimes_url = f'/api/agenda/{meeting_agenda_2.slug}/meetings/{meeting_type.slug}/datetimes/?user_external_id={user_external_id}'
+    meeting_agenda_3_datetimes_url = f'/api/agenda/{meeting_agenda_3.slug}/meetings/{meeting_type.slug}/datetimes/?user_external_id={user_external_id}'
+    virtual_agenda_datetimes_url = f'/api/agenda/{virtual_agenda.slug}/meetings/{meeting_type.slug}/datetimes/?user_external_id={user_external_id}'
+
+    today_at_15 = localtime(now()).replace(hour=15, minute=0)
+
+    # check all slots are free
+    resp = app.get(virtual_agenda_datetimes_url)
+    assert not any(x['disabled'] for x in resp.json['data'])
+    resp = app.get(meeting_agenda_1_datetimes_url)
+    assert not any(x['disabled'] for x in resp.json['data'])
+    resp = app.get(meeting_agenda_2_datetimes_url)
+    assert not any(x['disabled'] for x in resp.json['data'])
+    resp = app.get(meeting_agenda_3_datetimes_url)
+    assert not any(x['disabled'] for x in resp.json['data'])
+
+    for agenda in virtual_agenda.get_real_agendas():
+        meeting_event = Event.objects.create(
+            label='Event',
+            slug='meeting1',
+            start_datetime=today_at_15,
+            agenda=agenda,
+            places=1,
+            meeting_type=agenda.meetingtype_set.all()[0],
+            desk=agenda.desk_set.all()[0],
+        )
+        Booking.objects.create(event=meeting_event, user_external_id=user_external_id)
+
+        # now some slots are disabled
+        resp = app.get(virtual_agenda_datetimes_url)
+        assert any(x['disabled'] for x in resp.json['data'])
+        agenda_datetimes_url = f'/api/agenda/{agenda.slug}/meetings/{meeting_type.slug}/datetimes/?user_external_id={user_external_id}'
+        resp = app.get(agenda_datetimes_url)
+        assert any(x['disabled'] for x in resp.json['data'])
+        for other_agenda in virtual_agenda.get_real_agendas():
+            if other_agenda == agenda:
+                continue
+            other_agenda_datetimes_url = f'/api/agenda/{other_agenda.slug}/meetings/{meeting_type.slug}/datetimes/?user_external_id={user_external_id}'
+            resp = app.get(other_agenda_datetimes_url)
+            assert not any(x['disabled'] for x in resp.json['data'])
+
+        meeting_event.delete()