diff --git a/tests/test_api.py b/tests/test_api.py
index 2e9fbb6..0ee3e27 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -546,7 +546,7 @@ def dumps(self, obj, **kwargs):
                 return json.dumps(obj, **kwargs, cls=CustomJSONEncoder)
 
         class CustomSchema(ma.Schema):
-            custom_field = ma.fields.Field(load_default=CustomType())
+            custom_field = ma.fields.Raw(load_default=CustomType())
 
         app.config["OPENAPI_VERSION"] = openapi_version
         app.json = CustomJsonProvider(app)