diff --git a/demos/custom_auth.py b/demos/custom_auth.py
new file mode 100644
index 0000000..fd5c244
--- /dev/null
+++ b/demos/custom_auth.py
@@ -0,0 +1,21 @@
+import tornado.ioloop
+from tornado.web import RequestHandler, Application
+from tornado_http_auth import DigestAuthMixin, BasicAuthMixin, auth_required
+
+credentials = {"user1": "pass1"}
+
+
+class MainHandler(BasicAuthMixin, RequestHandler):
+    @auth_required(realm="Protected", auth_func=credentials.get)
+    def get(self):
+        self.write("Hello %s" % self._current_user)
+
+
+app = Application(
+    [
+        (r"/", MainHandler),
+    ]
+)
+
+app.listen(8888)
+tornado.ioloop.IOLoop.current().start()
diff --git a/demos/pam_auth.py b/demos/pam_auth.py
new file mode 100644
index 0000000..00ebdf8
--- /dev/null
+++ b/demos/pam_auth.py
@@ -0,0 +1,21 @@
+import tornado.ioloop
+from tornado.web import RequestHandler, Application
+from tornado_http_auth import DigestAuthMixin, BasicAuthMixin, auth_required
+
+import pamela
+
+
+class MainHandler(BasicAuthMixin, RequestHandler):
+    @auth_required(realm="Protected", auth_func=pamela.authenticate)
+    def get(self):
+        self.write("Hello %s" % self._current_user)
+
+
+app = Application(
+    [
+        (r"/", MainHandler),
+    ]
+)
+
+app.listen(8888)
+tornado.ioloop.IOLoop.current().start()
diff --git a/demos/requirements.txt b/demos/requirements.txt
new file mode 100644
index 0000000..77ab09d
--- /dev/null
+++ b/demos/requirements.txt
@@ -0,0 +1 @@
+pamela
diff --git a/tests/test_functional.py b/tests/test_functional.py
index d03680b..449762b 100644
--- a/tests/test_functional.py
+++ b/tests/test_functional.py
@@ -16,18 +16,28 @@ class BasicAuthHandler(BasicAuthMixin, RequestHandler):
     def get(self):
         self.write('Hello %s' % self._current_user)
 
+class BasicAuthWithPwdHandler(BasicAuthMixin, RequestHandler):
+    @auth_required(realm='Protected', auth_func=lambda u, p: p == credentials[u])
+    def get(self):
+        self.write('Hello %s' % self._current_user)
 
 class DigestAuthHandler(DigestAuthMixin, RequestHandler):
     @auth_required(realm='Protected', auth_func=credentials.get)
     def get(self):
         self.write('Hello %s' % self._current_user)
 
+class DigestAuthWithPwdHandler(DigestAuthMixin, RequestHandler):
+    @auth_required(realm='Protected', auth_func=lambda u, p: p == credentials[u])
+    def get(self):
+        self.write('Hello %s' % self._current_user)
 
 class AuthTest(AsyncHTTPTestCase):
     def get_app(self):
         urls = [
             ('/digest', DigestAuthHandler),
+            ('/digestpw', DigestAuthWithPwdHandler),
             ('/basic', BasicAuthHandler),
+            ('/basicpw', BasicAuthWithPwdHandler),
         ]
         return Application(urls, http_client=self.http_client)
 
@@ -36,6 +46,11 @@ def test_digest_auth(self):
         self.assertEqual(res.code, 401)
         # TODO: Add digest authentication to HTTPClient in order to test this.
 
+    def test_digest_auth_with_pw(self):
+        res = self.fetch('/digestpw')
+        self.assertEqual(res.code, 401)
+        # TODO: Add digest authentication to HTTPClient in order to test this.
+
     def test_basic_auth(self):
         res = self.fetch('/basic')
         self.assertEqual(res.code, 401)
@@ -46,3 +61,12 @@ def test_basic_auth(self):
         res = self.fetch('/basic', headers=hdr)
         self.assertEqual(res.code, 200)
 
+    def test_basic_auth_with_pw(self):
+        res = self.fetch('/basicpw')
+        self.assertEqual(res.code, 401)
+
+        auth = '%s:%s' % ('user1', 'pass1')
+        auth = b64encode(auth.encode('ascii'))
+        hdr = {'Authorization': 'Basic %s' % auth.decode('utf8')}
+        res = self.fetch('/basicpw', headers=hdr)
+        self.assertEqual(res.code, 200)
diff --git a/tornado_http_auth.py b/tornado_http_auth.py
index 2c6efbb..aefb298 100644
--- a/tornado_http_auth.py
+++ b/tornado_http_auth.py
@@ -1,12 +1,13 @@
 # Mostly everything in this module is inspired or outright copied from Twisted's cred.
 # https://github.com/twisted/twisted/blob/trunk/src/twisted/cred/credentials.py
-
+import inspect
 import os, re, sys
 import time
 import binascii
 import base64
 import hashlib
 
+import pamela
 from tornado.auth import AuthError
 
 
@@ -212,16 +213,34 @@ def authenticate_user(self, check_credentials_func, realm):
         auth_data = base64.b64decode(auth_data).decode('ascii')
         username, password = auth_data.split(':', 1)
 
-        challenge = check_credentials_func(username)
-        if not challenge:
-            raise self.SendChallenge()
+        # Here we keep backward compatibility with:
+        #   username -> password
+        # behavior, while also providing a
+        #   username, password -> Bool
+        # behavior for stricter authentication systems (PAM for instance)
+        loggedin = False
+
+        try:
+            challenge = check_credentials_func(username)
+            if not challenge:  # no password -> wrong username -> try again  (too nice to be safe ?)
+                raise self.SendChallenge()
+
+            loggedin = challenge == password
 
-        if challenge == password:
+        except (TypeError, pamela.PAMError):
+            # PAMError can occur because password is None by default, as pamela relies on PAM conversation interface...
+
+            try:
+                # password required, expect boolean return
+                loggedin = check_credentials_func(username, password)
+
+            except Exception:  # any exception here means wrong username / password combination -> try again
+                raise self.SendChallenge()
+
+        if loggedin:
             self._current_user = username
-            return True
-        else:
-            raise self.SendChallenge()
-        return False
+
+        return loggedin
 
 
 def auth_required(realm, auth_func):