diff --git a/src/function/sync/apply-actions/dispatch-app-logic-action/addusedtime2.ts b/src/function/sync/apply-actions/dispatch-app-logic-action/addusedtime2.ts
index 9f13263..d606814 100644
--- a/src/function/sync/apply-actions/dispatch-app-logic-action/addusedtime2.ts
+++ b/src/function/sync/apply-actions/dispatch-app-logic-action/addusedtime2.ts
@@ -17,6 +17,7 @@
 
 import * as Sequelize from 'sequelize'
 import { AddUsedTimeActionVersion2 } from '../../../../action'
+import { EventHandler } from '../../../../monitoring/eventhandler'
 import { MinuteOfDay } from '../../../../util/minuteofday'
 import { Cache } from '../cache'
 import { getRoundedTimestamp as getRoundedTimestampForUsedTime } from './addusedtime'
@@ -27,14 +28,34 @@ export const getRoundedTimestampForSessionDuration = () => {
   return now - (now % (1000 * 60 * 60 * 12 /* 12 hours */))
 }
 
-export async function dispatchAddUsedTimeVersion2 ({ deviceId, action, cache }: {
+export async function dispatchAddUsedTimeVersion2 ({ deviceId, action, cache, eventHandler }: {
   deviceId: string
   action: AddUsedTimeActionVersion2
   cache: Cache
+  eventHandler: EventHandler
 }) {
+  const deviceEntryUnsafe = await cache.database.device.findOne({
+    where: {
+      familyId: cache.familyId,
+      deviceId: deviceId
+    },
+    attributes: ['currentUserId'],
+    transaction: cache.transaction
+  })
+
+  if (!deviceEntryUnsafe) {
+    throw new Error('source device not found')
+  }
+
+  const deviceEntry = {
+    currentUserId: deviceEntryUnsafe.currentUserId
+  }
+
   const roundedTimestampForUsedTime = getRoundedTimestampForUsedTime().toString(10)
   const roundedTimestampForSessionDuration = getRoundedTimestampForSessionDuration().toString(10)
 
+  let addUsedTimeForADifferentUserThanTheCurrentUserOfTheDevice = false
+
   for (let i = 0; i < action.items.length; i++) {
     const item = action.items[i]
 
@@ -62,6 +83,10 @@ export async function dispatchAddUsedTimeVersion2 ({ deviceId, action, cache }:
       extraTimeInMillis: categoryEntryUnsafe.extraTimeInMillis
     }
 
+    if (categoryEntry.childId !== deviceEntry.currentUserId) {
+      addUsedTimeForADifferentUserThanTheCurrentUserOfTheDevice = true
+    }
+
     // tslint:disable-next-line:no-inner-declarations
     async function handle (start: number, end: number) {
       const lengthInMinutes = (end - start) + 1
@@ -174,5 +199,20 @@ export async function dispatchAddUsedTimeVersion2 ({ deviceId, action, cache }:
 
       cache.categoriesWithModifiedBaseData.push(item.categoryId)
     }
+
+    if (addUsedTimeForADifferentUserThanTheCurrentUserOfTheDevice) {
+      // there are two possible causes for this:
+      // - a device user was changed remotely while it was used by this user for
+      //   limited Apps (rarely)
+      // - a parent added time manually (rarely)
+      //
+      // For the second case, it's important to sync this change.
+      // As it should occur not too often, a full sync should be no problem.
+      // To keep an eye on it, it is counted.
+
+      cache.areChangesImportant = true
+
+      eventHandler.countEvent('add used time for a different user than the current user of the device')
+    }
   }
 }
diff --git a/src/function/sync/apply-actions/dispatch-app-logic-action/index.ts b/src/function/sync/apply-actions/dispatch-app-logic-action/index.ts
index f91deb3..7f26bf1 100644
--- a/src/function/sync/apply-actions/dispatch-app-logic-action/index.ts
+++ b/src/function/sync/apply-actions/dispatch-app-logic-action/index.ts
@@ -26,6 +26,7 @@ import {
   UpdateAppActivitiesAction,
   UpdateDeviceStatusAction
 } from '../../../../action'
+import { EventHandler } from '../../../../monitoring/eventhandler'
 import { Cache } from '../cache'
 import { dispatchAddInstalledApps } from './addinstalledapps'
 import { dispatchAddUsedTime } from './addusedtime'
@@ -36,17 +37,18 @@ import { dispatchTriedDisablingDeviceAdmin } from './trieddisablingdeviceadmin'
 import { dispatchUpdateAppActivities } from './updateappactivities'
 import { dispatchUpdateDeviceStatus } from './updatedevicestatus'
 
-export const dispatchAppLogicAction = async ({ action, deviceId, cache }: {
+export const dispatchAppLogicAction = async ({ action, deviceId, cache, eventHandler }: {
   action: AppLogicAction
   deviceId: string
   cache: Cache
+  eventHandler: EventHandler
 }) => {
   if (action instanceof AddInstalledAppsAction) {
     await dispatchAddInstalledApps({ deviceId, action, cache })
   } else if (action instanceof AddUsedTimeAction) {
     await dispatchAddUsedTime({ deviceId, action, cache })
   } else if (action instanceof AddUsedTimeActionVersion2) {
-    await dispatchAddUsedTimeVersion2({ deviceId, action, cache })
+    await dispatchAddUsedTimeVersion2({ deviceId, action, cache, eventHandler })
   } else if (action instanceof RemoveInstalledAppsAction) {
     await dispatchRemoveInstalledApps({ deviceId, action, cache })
   } else if (action instanceof SignOutAtDeviceAction) {
diff --git a/src/function/sync/apply-actions/index.ts b/src/function/sync/apply-actions/index.ts
index 16d812f..66b9da2 100644
--- a/src/function/sync/apply-actions/index.ts
+++ b/src/function/sync/apply-actions/index.ts
@@ -183,7 +183,8 @@ export const applyActionsFromDevice = async ({ database, request, websocket, con
             await dispatchAppLogicAction({
               action: parsedAction,
               cache,
-              deviceId: deviceEntry.deviceId
+              deviceId: deviceEntry.deviceId,
+              eventHandler
             })
           } catch (ex) {
             eventHandler.countEvent('applyActionsFromDevice actionWithError:' + parsedSerializedAction.type)