diff --git a/engine/apps/api/tests/test_schedules.py b/engine/apps/api/tests/test_schedules.py
index c788d521..cadcb5f4 100644
--- a/engine/apps/api/tests/test_schedules.py
+++ b/engine/apps/api/tests/test_schedules.py
@@ -424,6 +424,7 @@ def test_events_calendar(
                 "start": on_call_shift.start,
                 "end": on_call_shift.start + on_call_shift.duration,
                 "users": [{"display_name": user.username, "pk": user.public_primary_key}],
+                "missing_users": [],
                 "priority_level": on_call_shift.priority_level,
                 "source": "api",
                 "calendar_type": OnCallSchedule.PRIMARY,
@@ -487,6 +488,7 @@ def test_filter_events_calendar(
                 "start": mon_start,
                 "end": mon_start + on_call_shift.duration,
                 "users": [{"display_name": user.username, "pk": user.public_primary_key}],
+                "missing_users": [],
                 "priority_level": on_call_shift.priority_level,
                 "source": "api",
                 "calendar_type": OnCallSchedule.PRIMARY,
@@ -501,6 +503,7 @@ def test_filter_events_calendar(
                 "start": fri_start,
                 "end": fri_start + on_call_shift.duration,
                 "users": [{"display_name": user.username, "pk": user.public_primary_key}],
+                "missing_users": [],
                 "priority_level": on_call_shift.priority_level,
                 "source": "api",
                 "calendar_type": OnCallSchedule.PRIMARY,
@@ -567,6 +570,7 @@ def test_filter_events_range_calendar(
                 "start": fri_start,
                 "end": fri_start + on_call_shift.duration,
                 "users": [{"display_name": user.username, "pk": user.public_primary_key}],
+                "missing_users": [],
                 "priority_level": on_call_shift.priority_level,
                 "source": "api",
                 "calendar_type": OnCallSchedule.PRIMARY,
diff --git a/engine/apps/api/views/schedule.py b/engine/apps/api/views/schedule.py
index 06791a95..1de11b85 100644
--- a/engine/apps/api/views/schedule.py
+++ b/engine/apps/api/views/schedule.py
@@ -211,6 +211,7 @@ class ScheduleView(
                     }
                     for user in shift["users"]
                 ],
+                "missing_users": shift["missing_users"],
                 "priority_level": shift["priority"] if shift["priority"] != 0 else None,
                 "source": shift["source"],
                 "calendar_type": shift["calendar_type"],
diff --git a/engine/apps/schedules/ical_utils.py b/engine/apps/schedules/ical_utils.py
index 2705c4db..a22ddee4 100644
--- a/engine/apps/schedules/ical_utils.py
+++ b/engine/apps/schedules/ical_utils.py
@@ -137,6 +137,7 @@ def list_of_oncall_shifts_from_ical(
                     "start": g.start if g.start else datetime_start,
                     "end": g.end if g.end else datetime_end,
                     "users": [],
+                    "missing_users": [],
                     "priority": None,
                     "source": None,
                     "calendar_type": None,
@@ -157,6 +158,7 @@ def get_shifts_dict(calendar, calendar_type, schedule, datetime_start, datetime_
         priority = parse_priority_from_string(event.get(ICAL_SUMMARY, "[L0]"))
         pk, source = parse_event_uid(event.get(ICAL_UID))
         users = get_users_from_ical_event(event, schedule.organization)
+        missing_users = get_missing_users_from_ical_event(event, schedule.organization)
         # Define on-call shift out of ical event that has the actual user
         if len(users) > 0 or with_empty_shifts:
             if type(event[ICAL_DATETIME_START].dt) == datetime.date:
@@ -168,6 +170,7 @@ def get_shifts_dict(calendar, calendar_type, schedule, datetime_start, datetime_
                             "start": start,
                             "end": end,
                             "users": users,
+                            "missing_users": missing_users,
                             "priority": priority,
                             "source": source,
                             "calendar_type": calendar_type,
@@ -183,6 +186,7 @@ def get_shifts_dict(calendar, calendar_type, schedule, datetime_start, datetime_
                         "start": start,
                         "end": end,
                         "users": users,
+                        "missing_users": missing_users,
                         "priority": priority,
                         "source": source,
                         "calendar_type": calendar_type,
@@ -379,6 +383,14 @@ def get_usernames_from_ical_event(event):
     return usernames_found, priority
 
 
+def get_missing_users_from_ical_event(event, organization):
+    all_usernames, _ = get_usernames_from_ical_event(event)
+    users = list(get_users_from_ical_event(event, organization))
+    found_usernames = [u.username for u in users]
+    found_emails = [u.email for u in users]
+    return [u for u in all_usernames if u != "" and u not in found_usernames and u not in found_emails]
+
+
 def get_users_from_ical_event(event, organization):
     usernames_from_ical, _ = get_usernames_from_ical_event(event)
     users = []
diff --git a/grafana-plugin/src/models/schedule/schedule.types.ts b/grafana-plugin/src/models/schedule/schedule.types.ts
index 567be12b..dc3cc3f7 100644
--- a/grafana-plugin/src/models/schedule/schedule.types.ts
+++ b/grafana-plugin/src/models/schedule/schedule.types.ts
@@ -36,6 +36,7 @@ export interface ScheduleEvent {
   users: User[];
   is_empty: boolean;
   is_gap: boolean;
+  missing_users: string[];
 }
 
 export interface CreateScheduleExportTokenResponse {
diff --git a/grafana-plugin/src/pages/schedules/Schedules.tsx b/grafana-plugin/src/pages/schedules/Schedules.tsx
index ff557400..d538a81d 100644
--- a/grafana-plugin/src/pages/schedules/Schedules.tsx
+++ b/grafana-plugin/src/pages/schedules/Schedules.tsx
@@ -495,7 +495,15 @@ const Event = ({ event }: EventProps) => {
               ) : (
                 <HorizontalGroup spacing="sm">
                   <Icon style={{ color: PENDING_COLOR }} name="exclamation-triangle" />
-                  <Text type="secondary">Empty shift (event without associated user or user with Viewer access)</Text>
+                  <Text type="secondary">Empty shift</Text>
+                  {event.missing_users[0] && (
+                    <Text type="secondary">
+                      (check if {event.missing_users[0].includes(',') ? 'some of these users -' : 'user -'}{' '}
+                      <Text type="secondary">"{event.missing_users[0]}"</Text>{' '}
+                      {event.missing_users[0].includes(',') ? 'are' : 'is'} existing in OnCall or{' '}
+                      {event.missing_users[0].includes(',') ? 'have' : 'has'} Viewer role)
+                    </Text>
+                  )}
                 </HorizontalGroup>
               )}
               {event.source && <span> — source: {event.source}</span>}