diff --git a/src/addons/calendar/components/filter/filter.ts b/src/addons/calendar/components/filter/filter.ts
index 11ecb8eb8..9398c60b7 100644
--- a/src/addons/calendar/components/filter/filter.ts
+++ b/src/addons/calendar/components/filter/filter.ts
@@ -59,7 +59,7 @@ export class AddonCalendarFilterPopoverComponent implements OnInit {
      * Init the component.
      */
     ngOnInit(): void {
-        this.courseId = this.filter.courseId + '';
+        this.courseId = (this.filter.courseId || -1) + '';
     }
 
     /**