Index: /pyyaml/trunk/setup.py
===================================================================
--- /pyyaml/trunk/setup.py	(revision 364)
+++ /pyyaml/trunk/setup.py	(revision 376)
@@ -123,4 +123,6 @@
 
     def ext_status(self, ext):
+        if 'Java' in sys.version or 'IronPython' in sys.version or 'PyPy' in sys.version:
+            return False
         if isinstance(ext, Extension):
             with_ext = getattr(self, ext.attr_name)