diff --git a/NEWS b/NEWS
index 8fc14cd0..1b934b30 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,13 @@
 Current release
 ---------------
 
+What's new in psycopg 2.7.1
+---------------------------
+
+- Ignore `!None` arguments passed to `~psycopg2.connect()` and
+  `~psycopg2.extensions.make_dsn()` (:ticket:`#517`).
+
+
 What's new in psycopg 2.7
 -------------------------
 
diff --git a/lib/extensions.py b/lib/extensions.py
index 9fee5510..00d71f0a 100644
--- a/lib/extensions.py
+++ b/lib/extensions.py
@@ -162,6 +162,9 @@ def make_dsn(dsn=None, **kwargs):
                 "you can't specify both 'database' and 'dbname' arguments")
         kwargs['dbname'] = kwargs.pop('database')
 
+    # Drop the None arguments
+    kwargs = dict((k, v) for (k, v) in kwargs.iteritems() if v is not None)
+
     if dsn is not None:
         tmp = parse_dsn(dsn)
         tmp.update(kwargs)
diff --git a/tests/test_connection.py b/tests/test_connection.py
index a9525b4d..dae0560f 100755
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -459,6 +459,10 @@ class MakeDsnTestCase(ConnectingTestCase):
         dsn = ext.make_dsn(dsnin)
         self.assertEqual(dsn, dsnin)
 
+    def test_null_args(self):
+        dsn = ext.make_dsn("dbname=foo", user="bar", password=None)
+        self.assertDsnEqual(dsn, "dbname=foo user=bar")
+
     @skip_before_libpq(9, 2)
     def test_url_is_cool(self):
         url = 'postgresql://tester:secret@/test?application_name=wat'