diff --git a/lollipop/types.py b/lollipop/types.py
index 5535f19..7d8e1d3 100644
--- a/lollipop/types.py
+++ b/lollipop/types.py
@@ -1052,10 +1052,10 @@ def __init__(self, bases_or_fields=None, fields=None, constructor=None,
 
     @property
     def fields(self):
-        if not hasattr(self, '__fields'):
-            self.__fields = self._resolve_fields(self.bases, self._fields,
-                                                 self._only, self._exclude)
-        return self.__fields
+        if not hasattr(self, '_resolved_fields'):
+            self._resolved_fields = self._resolve_fields(self.bases, self._fields,
+                                                         self._only, self._exclude)
+        return self._resolved_fields
 
     default_field_type = inheritable_property('default_field_type')
     constructor = inheritable_property('constructor')