diff --git a/flashcards/serializers.py b/flashcards/serializers.py
index 1a6cb5a..f2f6f48 100644
--- a/flashcards/serializers.py
+++ b/flashcards/serializers.py
@@ -246,7 +246,7 @@ class QuizResponseSerializer(ModelSerializer):
 
     def to_representation(self, instance):
         return {
-            'pk': instance.user_flashcard.pk,
+            'pk': instance.pk,
             'section': instance.user_flashcard.flashcard.section.pk,
             'text': instance.user_flashcard.flashcard.text,
             'mask': self.mask