gistfile1.py

diff --git a/keystone/contrib/federation/utils.py b/keystone/contrib/federation/utils.py       
index 646ce99..577e2bb 100644
--- a/keystone/contrib/federation/utils.py
+++ b/keystone/contrib/federation/utils.py
@@ -169,7 +169,8 @@ class RuleProcessor(object):
         # semi-colon to indicate multiple values, i.e. groups.
         # This will create a new dictionary where the values are arrays, and
         # any multiple values are stored in the arrays.
-        assertion = dict((n, v.split(';')) for n, v in assertion_data.items())
+        assertion = dict((n, v.split(';')) for n, v in assertion_data.items()
+                         if isinstance(v, basestring))
         identity_values = [] 
 
         for rule in self.rules: