diff --git a/codeforlife/tests/model_view_set.py b/codeforlife/tests/model_view_set.py
index 4ce34499..855bbf02 100644
--- a/codeforlife/tests/model_view_set.py
+++ b/codeforlife/tests/model_view_set.py
@@ -729,7 +729,7 @@ def assert_serialized_model_equals_json_model(
         model_serializer = model_view_set.get_serializer(model)
 
         # Serialize the model.
-        serialized_model = model_serializer.data
+        serialized_model = dict(model_serializer.data)
 
         # Recursively convert all datetimes to strings.
         def datetime_values_to_representation(data: DataDict):
diff --git a/codeforlife/views/model.py b/codeforlife/views/model.py
index 14ed52fa..7a030507 100644
--- a/codeforlife/views/model.py
+++ b/codeforlife/views/model.py
@@ -183,9 +183,9 @@ def bulk_create(self, request: Request[RequestUser]):
         serializer.is_valid(raise_exception=True)
         self.perform_bulk_create(serializer)
         return Response(
-            serializer.data,
+            dict(serializer.data),
             status=status.HTTP_201_CREATED,
-            headers=self.get_success_headers(serializer.data),
+            headers=self.get_success_headers(dict(serializer.data)),
         )
 
     def perform_bulk_create(
@@ -224,7 +224,7 @@ def bulk_partial_update(self, request: Request[RequestUser]):
         )
         serializer.is_valid(raise_exception=True)
         self.perform_bulk_update(serializer)
-        return Response(serializer.data)
+        return Response(dict(serializer.data))
 
     def perform_bulk_update(
         self, serializer: "ModelListSerializer[RequestUser, AnyModel]"
@@ -303,7 +303,9 @@ def update(
             )
             serializer.is_valid(raise_exception=True)
             serializer.save()
-            return Response(**(response_kwargs or {}), data=serializer.data)
+            return Response(
+                **(response_kwargs or {}), data=dict(serializer.data)
+            )
 
         update.__name__ = name