diff --git a/categories/api/viewsets.py b/categories/api/viewsets.py
index 40fcaa1..d17e24c 100644
--- a/categories/api/viewsets.py
+++ b/categories/api/viewsets.py
@@ -6,6 +6,8 @@ from ..models import Category
 
 
 class CategorySerializer(serializers.ModelSerializer):
+    children = serializers.SerializerMethodField(method_name="_get_children")
+
     class Meta:
         model = Category
         fields = [
@@ -24,6 +26,10 @@ class CategorySerializer(serializers.ModelSerializer):
             "children",
         ]
 
+    def _get_children(self, obj):
+        children = obj.get_children()
+        return CategorySerializer(children, many=True).data
+
 
 countable_fields = [
     f
@@ -50,12 +56,6 @@ for field in countable_fields:
     CategorySerializer.Meta.fields += [f"{field.name}_count_cumulative"]
 
 
-CategorySerializer._declared_fields["children"] = CategorySerializer(
-    many=True,
-    source="get_children",
-)
-
-
 class CategoryList(list):  # To overcome problem with filters that require model in queryset
     model = Category