diff --git a/api/serializers/project.py b/api/serializers/project.py
index 9763e77e..e1177f1a 100644
--- a/api/serializers/project.py
+++ b/api/serializers/project.py
@@ -74,7 +74,8 @@ def update(self, instance, validated_data):
         Returns:
             Project: Het bijgewerkte project.
         """
-        validated_data.pop("max_groep_grootte", instance.max_groep_grootte)
+        validated_data.pop("max_groep_grootte", None)
+        validated_data.pop("project_groep", None)
 
         deadline = validated_data.pop("deadline", instance.deadline)
         extra_deadline = validated_data.pop("extra_deadline", instance.extra_deadline)