diff --git a/openapi.yaml b/openapi.yaml
index 7900e3d..56fd4f4 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -4138,6 +4138,7 @@ components:
             $ref: '#/components/schemas/GradeCount'
         averageGrade:
           type: number
+          nullable: true
           example: 18.01
       required: [ succeeded, failed, grades, averageGrade ]