diff --git a/functools.py b/functools.py
index a54f030..17b5d18 100644
--- a/functools.py
+++ b/functools.py
@@ -30,7 +30,8 @@ def update_wrapper(wrapper,
        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()