diff --git a/implementations/python/preserves/schema.py b/implementations/python/preserves/schema.py
index 965b742..5bef146 100644
--- a/implementations/python/preserves/schema.py
+++ b/implementations/python/preserves/schema.py
@@ -223,7 +223,7 @@ class Definition(SchemaObject):
         return not self.__eq__(other)
 
     def __hash__(self):
-        return hash(self._fields) ^ hash(self.__class_)
+        return hash(self._fields) ^ hash(self.__class__)
 
     def _accept(self, visitor):
         if self.VARIANT is None: