Index: Lib/test/test_sys.py
===================================================================
--- Lib/test/test_sys.py	(revision 70696)
+++ Lib/test/test_sys.py	(working copy)
@@ -221,6 +221,13 @@
             sys.setdlopenflags(oldflags)
 
     def test_refcount(self):
+        global n
+        # n must be a global in order for this test to
+        # pass while tracing with a python function.
+        # Tracing calls PyFrame_FastToLocals which
+        # will add a copy of any locals to the frame object,
+        # causing the reference count to increase by 2 instead
+        # of 1.
         self.assertRaises(TypeError, sys.getrefcount)
         c = sys.getrefcount(None)
         n = None