diff --git a/aria/modeling/utils.py b/aria/modeling/utils.py
index 1b6b375..27d261d 100644
--- a/aria/modeling/utils.py
+++ b/aria/modeling/utils.py
@@ -35,15 +35,14 @@
         # Just here to make sure Sphinx doesn't grab the base constructor's docstring
         super(ModelJSONEncoder, self).__init__(*args, **kwargs)
 
-    def default(self, o):                                                                           # pylint: disable=method-hidden
-        from .mixins import ModelMixin
-        if isinstance(o, ModelMixin):
+    def default(self, o):  # pylint: disable=method-hidden
+        try:
             if hasattr(o, 'value'):
                 dict_to_return = o.to_dict(fields=('value',))
                 return dict_to_return['value']
             else:
                 return o.to_dict()
-        else:
+        except AttributeError:
             return JSONEncoder.default(self, o)