diff --git a/mandaye/backends/ldap_back.py b/mandaye/backends/ldap_back.py
index 6eaaf73..9eac07a 100644
--- a/mandaye/backends/ldap_back.py
+++ b/mandaye/backends/ldap_back.py
@@ -106,11 +106,17 @@ class Association(object):
             logger.info("New association %r with %r", sp_login, idp_unique_id)
             return unique_id
         else:
-            dn = results[0][0]
+            biggest = '0'
+            biggest_pos = 0
+            for i, result in enumerate(results):
+                if result[1]['lastConnectionDate'][0] > biggest:
+                    biggest = result[1]['lastConnectionDate'][0]
+                    biggest_pos = i
+            dn = results[biggest_pos][0]
             mod_list = [(ldap.MOD_REPLACE, 'spPostValues', json.dumps(sp_post_values))]
             storage_conn.modify_s(dn, mod_list)
             logger.info("Update post values for %r (%r)", sp_login, idp_unique_id)
-        return results[0][1]['uniqueID'][0]
+            return results[biggest_pos][1]['uniqueID'][0]
 
     @staticmethod
     def delete(asso_id):
@@ -127,7 +133,13 @@ class Association(object):
         results = storage_conn.search_s(config.ldap_base_dn, ldap.SCOPE_ONELEVEL,
                 filterstr='(&(objectClass=MandayeUser)(spName=%s)(idpUniqueID=%s)(idpName=%s))' % (sp_name, idp_unique_id, idp_name))
         if results:
-            return Association.ldap2association(results[0][1])
+            biggest = '0'
+            biggest_pos = 0
+            for i, result in enumerate(results):
+                if result[1]['lastConnectionDate'][0] > biggest:
+                    biggest = result[1]['lastConnectionDate'][0]
+                    biggest_pos = i
+            return Association.ldap2association(results[biggest_pos][1])
         return None
 
     @staticmethod