diff --git a/README.rst b/README.rst
index ed0b216..ac2f1bf 100644
--- a/README.rst
+++ b/README.rst
@@ -96,8 +96,9 @@ An event is triggered when one of the multiple policies configured is selected.
 
     # Track policy used, for prefixing user_id and for logging.
     def on_policy_selected(event):
-        print("%s (%s) was selected for request %s" % (event.policy_name,
-                                                       event.policy,
-                                                       event.request))
+        print("%s (%s) authenticated %s for request %s" % (event.policy_name,
+                                                           event.policy,
+                                                           event.userid,
+                                                           event.request))
 
     config.add_subscriber(on_policy_selected, MultiAuthPolicySelected)
diff --git a/pyramid_multiauth/__init__.py b/pyramid_multiauth/__init__.py
index 0b488da..1440286 100644
--- a/pyramid_multiauth/__init__.py
+++ b/pyramid_multiauth/__init__.py
@@ -37,10 +37,11 @@ def track_policy(event):
             print("We selected policy %s" % event.policy)
 
     """
-    def __init__(self, policy, request):
+    def __init__(self, policy, request, userid=None):
         self.policy = policy
         self.policy_name = getattr(policy, "_pyramid_multiauth_name", None)
         self.request = request
+        self.userid = userid
 
 
 @implementer(IAuthenticationPolicy)
@@ -77,7 +78,8 @@ def authenticated_userid(self, request):
             userid = policy.authenticated_userid(request)
             if userid is not None:
                 request.registry.notify(MultiAuthPolicySelected(policy,
-                                                                request))
+                                                                request,
+                                                                userid))
 
                 if self._callback is None:
                     break
@@ -117,6 +119,9 @@ def effective_principals(self, request):
                 userid = policy.authenticated_userid(request)
                 if userid is None:
                     continue
+                request.registry.notify(MultiAuthPolicySelected(policy,
+                                                                request,
+                                                                userid))
                 groups = self._callback(userid, request)
                 if groups is not None:
                     break
diff --git a/pyramid_multiauth/tests.py b/pyramid_multiauth/tests.py
index 3b6f7b3..bacd21c 100644
--- a/pyramid_multiauth/tests.py
+++ b/pyramid_multiauth/tests.py
@@ -198,9 +198,17 @@ def track_policy(event):
 
             self.assertEquals(selected_policy[0].policy, policies[0])
             self.assertEquals(selected_policy[0].policy_name, "name")
+            self.assertEquals(selected_policy[0].userid, "test2")
             self.assertEquals(selected_policy[0].request, request)
             self.assertEquals(len(selected_policy), 1)
 
+            # Effective principals also triggers an event when groupfinder
+            # is provided.
+            policy_with_group = MultiAuthenticationPolicy(policies,
+                                                          lambda u, r: ['foo'])
+            policy_with_group.effective_principals(request)
+            self.assertEquals(len(selected_policy), 2)
+
     def test_stacking_of_unauthenticated_userid(self):
         policies = [TestAuthnPolicy2(), TestAuthnPolicy3()]
         policy = MultiAuthenticationPolicy(policies)