diff --git a/pgpasslib.py b/pgpasslib.py
index 3cfd221..84c3cb6 100644
--- a/pgpasslib.py
+++ b/pgpasslib.py
@@ -38,13 +38,11 @@
 DEFAULT_HOST = 'localhost'
 DEFAULT_PORT = 5432
 DEFAULT_USER = stdlib_getpass.getuser()
-DEFAULT_DBNAME = DEFAULT_USER
 
 PATTERN = re.compile(r'^(.*):(.*):(.*):(.*):(.*)$', re.MULTILINE)
 
 
-def getpass(host=DEFAULT_HOST, port=DEFAULT_PORT, dbname=DEFAULT_DBNAME,
-            user=DEFAULT_USER):
+def getpass(host, port, dbname, user):
     """Return the password for the specified host, port, dbname and user.
     :py:const:`None` will be returned if a password can not be found for the
     specified  connection parameters.
@@ -70,6 +68,19 @@ def getpass(host=DEFAULT_HOST, port=DEFAULT_PORT, dbname=DEFAULT_DBNAME,
     :raises: InvalidEntry
 
     """
+
+    if not host:
+        host = DEFAULT_HOST
+
+    if not port:
+        port = DEFAULT_PORT
+
+    if not user:
+        user = DEFAULT_USER
+
+    if not dbname:
+        dbname = user
+
     if not isinstance(port, int):
         port = int(port)
     for entry in _get_entries():
diff --git a/tests.py b/tests.py
index f4f68cd..c0f8dc1 100644
--- a/tests.py
+++ b/tests.py
@@ -204,6 +204,18 @@ def test_no_match_on_host(self):
         self.assertFalse(self.entry.match('foo', 6000, 'bar', 'qux'))
 
 
+class GetpassDefaultsTest(unittest.TestCase):
+
+    def setUp(self):
+        self.entry = pgpasslib._Entry('localhost', 5432, '*', 'mydb', 'mypass')
+
+    def test_match_on_port_none(self):
+        self.assertTrue(self.entry.match('localhost', None, 'mydb', 'mydb'))
+
+    def test_match_on_default_db(self):
+        self.assertTrue(self.entry.match('localhost', None, None, 'mydb'))
+
+
 class GetPassMatch1Test(unittest.TestCase):
 
     def test_getpass_returns_expected_result(self):