diff --git a/app/services/grade_service.ts b/app/services/grade_service.ts
index 59e7db1..ddf8ffb 100644
--- a/app/services/grade_service.ts
+++ b/app/services/grade_service.ts
@@ -44,6 +44,7 @@ export class GradeService {
       .where('studentId', userId)
       .where('date', '>=', startDate.toJSDate())
       .where('date', '<', endDate.toJSDate())
+      .whereNotNull('garde')
       .preload('subject')
       .orderBy('date', 'asc')
   }
@@ -53,6 +54,7 @@ export class GradeService {
       .where('studentId', userId)
       .where('subjectId', subjectId)
       .where('date', '<', beforeDate.toJSDate())
+      .whereNotNull('garde')
     return colles.length ? this.calculateAverage(colles) : 0
   }