diff --git a/src/addons/calendar/components/calendar/calendar.ts b/src/addons/calendar/components/calendar/calendar.ts
index 1e8bf8d73..aef2a3a74 100644
--- a/src/addons/calendar/components/calendar/calendar.ts
+++ b/src/addons/calendar/components/calendar/calendar.ts
@@ -340,7 +340,9 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
     ngOnDestroy(): void {
         this.undeleteEventObserver?.off();
         this.manager?.destroy();
-        this.managerUnsubscribe && this.managerUnsubscribe();
+        this.managerUnsubscribe?.();
+
+        delete this.manager;
     }
 
 }
diff --git a/src/addons/calendar/pages/day/day.page.ts b/src/addons/calendar/pages/day/day.page.ts
index 839a3a7d5..3c266ee85 100644
--- a/src/addons/calendar/pages/day/day.page.ts
+++ b/src/addons/calendar/pages/day/day.page.ts
@@ -457,7 +457,9 @@ export class AddonCalendarDayPage implements OnInit, OnDestroy {
         this.filterChangedObserver?.off();
         this.manager?.getSource().forgetRelatedSources();
         this.manager?.destroy();
-        this.managerUnsubscribe && this.managerUnsubscribe();
+        this.managerUnsubscribe?.();
+
+        delete this.manager;
     }
 
 }
diff --git a/src/addons/mod/book/pages/contents/contents.ts b/src/addons/mod/book/pages/contents/contents.ts
index fef0d3775..9c290473e 100644
--- a/src/addons/mod/book/pages/contents/contents.ts
+++ b/src/addons/mod/book/pages/contents/contents.ts
@@ -314,8 +314,10 @@ export class AddonModBookContentsPage implements OnInit, OnDestroy {
      * @inheritdoc
      */
     ngOnDestroy(): void {
-        this.managerUnsubscribe && this.managerUnsubscribe();
         this.manager?.destroy();
+        this.managerUnsubscribe?.();
+
+        delete this.manager;
     }
 
 }