Index: Lib/test/test_functools.py
===================================================================
--- Lib/test/test_functools.py	(revision 77513)
+++ Lib/test/test_functools.py	(working copy)
@@ -266,7 +266,24 @@
         self.assertEqual(wrapper.attr, 'This is a different test')
         self.assertEqual(wrapper.dict_attr, f.dict_attr)
 
+    def test_wraps_missing_attributes(self):
 
+        def testme():
+            pass
+
+        # sanity check
+        self.assert_(not hasattr(testme, 'contrived_attribute'))
+
+        assigned = functools.WRAPPER_ASSIGNMENTS + ('contrived_attribute',)
+        @functools.wraps(testme, assigned=assigned)
+        def wrapper():
+            pass
+
+        # if everything worked as expected, @functools.wraps will have copied
+        # over the usual attribute assignments, and silently skipped the missing
+        # "contrived_attribute" attribute
+        self.check_wrapper(wrapper, testme, assigned=functools.WRAPPER_ASSIGNMENTS)
+
 class TestReduce(unittest.TestCase):
 
     def test_reduce(self):
Index: Lib/functools.py
===================================================================
--- Lib/functools.py	(revision 77513)
+++ Lib/functools.py	(working copy)
@@ -30,7 +30,8 @@
        function (defaults to functools.WRAPPER_UPDATES)
     """
     for attr in assigned:
-        setattr(wrapper, attr, getattr(wrapped, attr))
+        if hasattr(wrapped, attr):
+            setattr(wrapper, attr, getattr(wrapped, attr))
     for attr in updated:
         getattr(wrapper, attr).update(getattr(wrapped, attr, {}))
     # Return the wrapper so this can be used as a decorator via partial()