diff --git a/AUTHORS b/AUTHORS
index 5f42f8565..a0aa707c7 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -32,5 +32,6 @@ Contributors are:
 -A. Jesse Jiryu Davis <jesse _at_ emptysquare.net>
 -Steven Whitman <ninloot _at_ gmail.com>
 -Stefan Stancu <stefan.stancu _at_ gmail.com>
+-César Izurieta <cesar _at_ caih.org>
 
 Portions derived from other open source works and are clearly marked.
diff --git a/git/util.py b/git/util.py
index 3ba588577..7ca0564eb 100644
--- a/git/util.py
+++ b/git/util.py
@@ -864,9 +864,12 @@ def __init__(self, id_attr, prefix=''):
 
     def __contains__(self, attr):
         # first try identity match for performance
-        rval = list.__contains__(self, attr)
-        if rval:
-            return rval
+        try:
+            rval = list.__contains__(self, attr)
+            if rval:
+                return rval
+        except (AttributeError, TypeError):
+            pass
         # END handle match
 
         # otherwise make a full name search