diff --git a/src/addon/mod/workshop/providers/prefetch-handler.ts b/src/addon/mod/workshop/providers/prefetch-handler.ts
index 5168d2a5e..651e1b735 100644
--- a/src/addon/mod/workshop/providers/prefetch-handler.ts
+++ b/src/addon/mod/workshop/providers/prefetch-handler.ts
@@ -224,9 +224,9 @@ export class AddonModWorkshopPrefetchHandler extends CoreCourseActivityPrefetchH
      * @param  {number}  workshopId Workshop ID.
      * @param  {any[]}   groups     Array of groups in the activity.
      * @param  {string}  siteId     Site ID. If not defined, current site.
-     * @return {Promise<any>}       All unique entries.
+     * @return {Promise<any[]>}       All unique entries.
      */
-    protected getAllGradesReport(workshopId: number, groups: any[], siteId: string): Promise<any> {
+    protected getAllGradesReport(workshopId: number, groups: any[], siteId: string): Promise<any[]> {
         const promises = [];
 
         groups.forEach((group) => {
@@ -245,7 +245,7 @@ export class AddonModWorkshopPrefetchHandler extends CoreCourseActivityPrefetchH
                 });
             });
 
-            return uniqueGrades;
+            return this.utils.objectToArray(uniqueGrades);
         });
     }