https://github.com/nose-devs/nose/commit/43c35e49106916f51f676455888fe7a39d030113.diff
diff --git a/nose/pyversion.py b/nose/pyversion.py
index fba5ada..8b56614 100644
--- a/nose/pyversion.py
+++ b/nose/pyversion.py
@@ -89,7 +89,8 @@ def __init__(self, cls, func):
         self.__dict__ = func.__dict__.copy()
         self._func = func
         self.__self__ = UnboundSelf(cls)
-        self.im_class = cls
+        if sys.version_info < (3, 0):
+            self.im_class = cls
 
     def address(self):
         cls = self.__self__.cls