diff --git a/web/src/lib/managers/timeline-manager/group-insertion-cache.svelte.ts b/web/src/lib/managers/timeline-manager/group-insertion-cache.svelte.ts
index 0fdf18e302..66cca61d45 100644
--- a/web/src/lib/managers/timeline-manager/group-insertion-cache.svelte.ts
+++ b/web/src/lib/managers/timeline-manager/group-insertion-cache.svelte.ts
@@ -1,4 +1,4 @@
-import type { TimelinePlainDate } from '$lib/utils/timeline-util';
+import { setDifference, type TimelinePlainDate } from '$lib/utils/timeline-util';
 import { AssetOrder } from '@immich/sdk';
 import type { DayGroup } from './day-group.svelte';
 import type { MonthGroup } from './month-group.svelte';
@@ -27,7 +27,7 @@ export class GroupInsertionCache {
   }
 
   get existingDayGroups() {
-    return this.changedDayGroups.difference(this.newDayGroups);
+    return setDifference(this.changedDayGroups, this.newDayGroups);
   }
 
   get updatedBuckets() {
diff --git a/web/src/lib/managers/timeline-manager/internal/operations-support.svelte.ts b/web/src/lib/managers/timeline-manager/internal/operations-support.svelte.ts
index 9a45b821f1..82ec78499b 100644
--- a/web/src/lib/managers/timeline-manager/internal/operations-support.svelte.ts
+++ b/web/src/lib/managers/timeline-manager/internal/operations-support.svelte.ts
@@ -1,4 +1,4 @@
-import type { TimelinePlainDate } from '$lib/utils/timeline-util';
+import { setDifference, type TimelinePlainDate } from '$lib/utils/timeline-util';
 import { AssetOrder } from '@immich/sdk';
 
 import { GroupInsertionCache } from '../group-insertion-cache.svelte';
@@ -76,7 +76,7 @@ export function runAssetOperation(
       if (moveAssets.length > 0) {
         combinedMoveAssets.push(moveAssets);
       }
-      idsToProcess = idsToProcess.difference(processedIds);
+      idsToProcess = setDifference(idsToProcess, processedIds);
       for (const id of processedIds) {
         idsProcessed.add(id);
       }
diff --git a/web/src/lib/managers/timeline-manager/month-group.svelte.ts b/web/src/lib/managers/timeline-manager/month-group.svelte.ts
index 9a19429c49..f18a1e6413 100644
--- a/web/src/lib/managers/timeline-manager/month-group.svelte.ts
+++ b/web/src/lib/managers/timeline-manager/month-group.svelte.ts
@@ -9,6 +9,7 @@ import {
   fromTimelinePlainDateTime,
   fromTimelinePlainYearMonth,
   getTimes,
+  setDifference,
   type TimelinePlainDateTime,
   type TimelinePlainYearMonth,
 } from '$lib/utils/timeline-util';
@@ -132,7 +133,7 @@ export class MonthGroup {
         if (moveAssets.length > 0) {
           combinedMoveAssets.push(moveAssets);
         }
-        idsToProcess = idsToProcess.difference(processedIds);
+        idsToProcess = setDifference(idsToProcess, processedIds);
         for (const id of processedIds) {
           idsProcessed.add(id);
         }
diff --git a/web/src/lib/utils/timeline-util.ts b/web/src/lib/utils/timeline-util.ts
index ce67355c12..c3e41c01be 100644
--- a/web/src/lib/utils/timeline-util.ts
+++ b/web/src/lib/utils/timeline-util.ts
@@ -216,3 +216,13 @@ export const plainDateTimeCompare = (ascending: boolean, a: TimelinePlainDateTim
   }
   return aDateTime.millisecond - bDateTime.millisecond;
 };
+
+export function setDifference<T>(setA: Set<T>, setB: Set<T>): Set<T> {
+  const result = new Set<T>();
+  for (const value of setA) {
+    if (!setB.has(value)) {
+      result.add(value);
+    }
+  }
+  return result;
+}