diff --git a/social_core/backends/saml.py b/social_core/backends/saml.py
index 985d37ed..104505d9 100644
--- a/social_core/backends/saml.py
+++ b/social_core/backends/saml.py
@@ -79,7 +79,7 @@ def get_attr(self, attributes, conf_key, default_attribute):
             if len(value):
                 value = value[0]
             else:
-                value = None
+                value = ''
         return value
 
     @property