diff --git a/components/TableScheduleEventSlots.vue b/components/TableScheduleEventSlots.vue
index e3d6650..8de0988 100644
--- a/components/TableScheduleEventSlots.vue
+++ b/components/TableScheduleEventSlots.vue
@@ -123,7 +123,7 @@
 								<button
 									v-if="es.slot.isModified()"
 									type="button"
-									@click="es.event.discardSlot(es.slot.id)"
+									@click="schedule.discardEventSlot(es.slot.id)"
 								>Revert</button>
 							</td>
 						</template>
diff --git a/components/TableScheduleShiftSlots.vue b/components/TableScheduleShiftSlots.vue
index 09a45a0..dddb5e2 100644
--- a/components/TableScheduleShiftSlots.vue
+++ b/components/TableScheduleShiftSlots.vue
@@ -124,7 +124,7 @@
 								<button
 									v-if="ss.slot.isModified()"
 									type="button"
-									@click="ss.shift.discardSlot(ss.slot.id)"
+									@click="schedule.discardShiftSlot(ss.slot.id)"
 								>Revert</button>
 							</td>
 						</template>
diff --git a/utils/client-schedule.ts b/utils/client-schedule.ts
index d0d78d6..1e64a19 100644
--- a/utils/client-schedule.ts
+++ b/utils/client-schedule.ts
@@ -197,19 +197,6 @@ export class ClientScheduleEvent extends ClientEntity<ApiScheduleEvent> {
 		}
 	}
 
-	discardSlot(id: Id) {
-		if (!this.slotIds.has(id)) {
-			throw new Error("ClientScheduleEvent.discardSlot: slot does not exist");
-		}
-		const slot = this.schedule.eventSlots.get(id)!;
-		if (slot.isNewEntity) {
-			this.slotIds.delete(id);
-			this.schedule.eventSlots.delete(id);
-		} else {
-			slot.discard();
-		}
-	}
-
 	static create(
 		schedule: ClientSchedule,
 		id: Id,
@@ -300,7 +287,7 @@ export class ClientScheduleEvent extends ClientEntity<ApiScheduleEvent> {
 export class ClientScheduleEventSlot {
 	schedule!: ClientSchedule;
 	serverDeleted: boolean;
-	serverEventId: Id;
+	serverEventId: Id | undefined;
 	serverStart: DateTime;
 	serverEnd: DateTime;
 	serverLocationIds: Set<Id>;
@@ -311,7 +298,7 @@ export class ClientScheduleEventSlot {
 		public id: Id,
 		public isNewEntity: boolean,
 		public deleted: boolean,
-		public eventId: Id,
+		public eventId: Id | undefined,
 		public start: DateTime,
 		public end: DateTime,
 		public locationIds: Set<Id>,
@@ -341,11 +328,11 @@ export class ClientScheduleEventSlot {
 		);
 	}
 
-	setEventId(newEventId: Id) {
+	setEventId(newEventId: Id | undefined) {
 		if (this.eventId === newEventId)
 			return;
-		this.schedule.events.get(newEventId)!.slotIds.add(this.id);
-		this.schedule.events.get(this.eventId)!.slotIds.delete(this.id);
+		this.schedule.events.get(newEventId!)?.slotIds.add(this.id);
+		this.schedule.events.get(this.eventId!)?.slotIds.delete(this.id);
 		this.eventId = newEventId;
 	}
 
@@ -582,19 +569,6 @@ export class ClientScheduleShift extends ClientEntity<ApiScheduleShift> {
 		}
 	}
 
-	discardSlot(id: Id) {
-		if (!this.slotIds.has(id)) {
-			throw new Error("ClientScheduleShift.discardSlot: slot does not exist");
-		}
-		const slot = this.schedule.shiftSlots.get(id)!;
-		if (slot.isNewEntity) {
-			this.slotIds.delete(id);
-			this.schedule.shiftSlots.delete(id);
-		} else {
-			slot.discard();
-		}
-	}
-
 	static create(
 		schedule: ClientSchedule,
 		id: Id,
@@ -670,7 +644,7 @@ export class ClientScheduleShift extends ClientEntity<ApiScheduleShift> {
 export class ClientScheduleShiftSlot {
 	schedule!: ClientSchedule;
 	serverDeleted: boolean;
-	serverShiftId: Id;
+	serverShiftId: Id | undefined;
 	serverStart: DateTime;
 	serverEnd: DateTime;
 	serverAssigned: Set<Id>;
@@ -679,7 +653,7 @@ export class ClientScheduleShiftSlot {
 		public id: Id,
 		public isNewEntity: boolean,
 		public deleted: boolean,
-		public shiftId: Id,
+		public shiftId: Id | undefined,
 		public start: DateTime,
 		public end: DateTime,
 		public assigned: Set<Id>,
@@ -703,11 +677,11 @@ export class ClientScheduleShiftSlot {
 		);
 	}
 
-	setShiftId(newShiftId: Id) {
+	setShiftId(newShiftId: Id | undefined) {
 		if (this.shiftId === newShiftId)
 			return;
-		this.schedule.shifts.get(newShiftId)!.slotIds.add(this.id);
-		this.schedule.shifts.get(this.shiftId)!.slotIds.delete(this.id);
+		this.schedule.shifts.get(newShiftId!)?.slotIds.add(this.id);
+		this.schedule.shifts.get(this.shiftId!)?.slotIds.delete(this.id);
 		this.shiftId = newShiftId;
 	}
 
@@ -823,6 +797,39 @@ export class ClientSchedule extends ClientEntity<ApiSchedule> {
 		this.shifts.discard();
 	}
 
+	discardEventSlot(id: Id) {
+		const eventSlot = this.eventSlots.get(id);
+		if (!eventSlot) {
+			throw new Error("ClientSchedule.discardEventSlot: slot does not exist");
+		}
+		if (eventSlot.isNewEntity) {
+			this.eventSlots.delete(id);
+			if (eventSlot.eventId !== undefined)
+				this.events.get(eventSlot.eventId)?.slotIds.delete(id);
+			if (eventSlot.serverEventId !== undefined && eventSlot.serverEventId !== eventSlot.eventId)
+				this.events.get(eventSlot.serverEventId)?.schedule.eventSlots.delete(id);
+		} else {
+			eventSlot.discard();
+		}
+	}
+
+	discardShiftSlot(id: Id) {
+		const shiftSlot = this.shiftSlots.get(id);
+		if (!shiftSlot) {
+			throw new Error("ClientSchedule.discardShiftSlot: slot does not exist");
+		}
+		if (shiftSlot.isNewEntity) {
+			this.shiftSlots.delete(id);
+			if (shiftSlot.shiftId !== undefined)
+				this.shifts.get(shiftSlot.shiftId)?.slotIds.delete(id);
+			if (shiftSlot.serverShiftId !== undefined && shiftSlot.serverShiftId !== shiftSlot.shiftId)
+				this.shifts.get(shiftSlot.serverShiftId)?.schedule.shiftSlots.delete(id);
+		} else {
+			shiftSlot.discard();
+		}
+	}
+
+
 	override isModified() {
 		return (
 			super.isModified()