diff --git a/src/saml2/assertion.py b/src/saml2/assertion.py
index ad08345..86def2e 100644
--- a/src/saml2/assertion.py
+++ b/src/saml2/assertion.py
@@ -78,7 +78,8 @@ def _match(attr, ava):
     return None
 
 
-def filter_on_attributes(ava, required=None, optional=None, acs=None):
+def filter_on_attributes(ava, required=None, optional=None, acs=None,
+                         fail_on_unfulfilled_requirements=True):
     """ Filter
     
     :param ava: An attribute value assertion as a dictionary
@@ -86,6 +87,8 @@ def filter_on_attributes(ava, required=None, optional=None, acs=None):
         required
     :param optional: list of RequestedAttribute instances defined to be
         optional
+    :param fail_on_unfulfilled_requirements: If required attributes
+        are missing fail or fail not depending on this parameter.
     :return: The modified attribute value assertion
     """
     res = {}
@@ -116,7 +119,7 @@ def filter_on_attributes(ava, required=None, optional=None, acs=None):
                 values = []
             res[_fn] = _filter_values(ava[_fn], values, True)
             continue
-        else:
+        elif fail_on_unfulfilled_requirements:
             desc = "Required attribute missing: '%s' (%s)" % (attr["name"],
                                                               _name)
             raise MissingValue(desc)
@@ -434,6 +437,16 @@ class Policy(object):
 
         return self.get("attribute_restrictions", sp_entity_id)
 
+    def get_fail_on_missing_requested(self, sp_entity_id):
+        """ Return the whether the IdP should should fail if the SPs
+        requested attributes could not be found.
+
+        :param sp_entity_id: The SP entity ID
+        :return: The restrictions
+        """
+
+        return self.get("fail_on_missing_requested", sp_entity_id, True)
+
     def entity_category_attributes(self, ec):
         if not self._restrictions:
             return None
@@ -492,7 +505,9 @@ class Policy(object):
         
         if required or optional:
             logger.debug("required: %s, optional: %s" % (required, optional))
-            ava = filter_on_attributes(ava, required, optional, self.acs)
+            ava = filter_on_attributes(
+                ava, required, optional, self.acs,
+                self.get_fail_on_missing_requested(sp_entity_id))
         
         return ava
     
diff --git a/src/saml2/config.py b/src/saml2/config.py
index 1a96f16..4dc6f21 100644
--- a/src/saml2/config.py
+++ b/src/saml2/config.py
@@ -269,7 +269,8 @@ class Config(object):
                 acs = ac_factory()
 
             if not acs:
-                raise ConfigurationError("No attribute converters, something is wrong!!")
+                raise ConfigurationError(
+                    "No attribute converters, something is wrong!!")
 
             _acs = self.getattr("attribute_converters", typ)
             if _acs:
diff --git a/tests/test_20_assertion.py b/tests/test_20_assertion.py
index 4c65438..820b2da 100644
--- a/tests/test_20_assertion.py
+++ b/tests/test_20_assertion.py
@@ -172,6 +172,8 @@ def test_ava_filter_2():
            "surName": "Jeter",
            "mail": "derek@example.com"}
 
+    # mail removed because it doesn't match the regular expression
+    # So this should fail.
     raises(MissingValue, policy.filter, ava, 'urn:mace:umu.se:saml:roland:sp',
            None, [mail], [gn, sn])
 
@@ -183,6 +185,44 @@ def test_ava_filter_2():
            None, [gn, sn, mail])
 
 
+def test_ava_filter_dont_fail():
+    conf = {
+        "default": {
+            "lifetime": {"minutes": 15},
+            "attribute_restrictions": None,  # means all I have
+        },
+        "urn:mace:umu.se:saml:roland:sp": {
+            "lifetime": {"minutes": 5},
+            "attribute_restrictions": {
+                "givenName": None,
+                "surName": None,
+                "mail": [".*@.*\.umu\.se"],
+            },
+            "fail_on_missing_requested": False
+        }}
+
+    policy = Policy(conf)
+
+    ava = {"givenName": "Derek",
+           "surName": "Jeter",
+           "mail": "derek@example.com"}
+
+    # mail removed because it doesn't match the regular expression
+    # So it should fail if the 'fail_on_ ...' flag wasn't set
+    _ava = policy.filter(ava,'urn:mace:umu.se:saml:roland:sp', None,
+                         [mail], [gn, sn])
+
+    assert _ava
+
+    ava = {"givenName": "Derek",
+           "surName": "Jeter"}
+
+    # it wasn't there to begin with
+    _ava = policy.filter(ava, 'urn:mace:umu.se:saml:roland:sp',
+                         None, [gn, sn, mail])
+
+    assert _ava
+
 def test_filter_attribute_value_assertions_0(AVA):
     p = Policy({
         "default": {
@@ -802,4 +842,4 @@ def test_assertion_with_authn_instant():
 
 
 if __name__ == "__main__":
-    test_assertion_2()
+    test_ava_filter_dont_fail()