mark test depending on ref counting
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 67de20e..a60107b 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -48,6 +48,7 @@
         os.closerange(first, first + 2)
         self.assertRaises(OSError, os.write, first, "a")
 
+    @test_support.cpython_only
     def test_rename(self):
         path = unicode(test_support.TESTFN)
         old = sys.getrefcount(path)