diff --git a/CHANGES.txt b/CHANGES.txt
index e2f41df..c4c1d36 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -4,11 +4,15 @@ Unreleased
 Bug Fixes
 ~~~~~~~~~
 
+- Time of "00:00" no longer gives ``colander.Invalid``.
+
 - Un-break wrapping of callable instances as ``colander.deferred``.
   See https://github.com/Pylons/colander/issues/141.
+
 - Set the max length TLD to 22 in ``Email`` validator based on the
   current list of valid TLDs.
   See https://github.com/Pylons/colander/issues/159
+
 - Fix an issue where ``drop`` was not recognized as a default and was
   returning the ``drop`` instance instead of omitting the value.
   https://github.com/Pylons/colander/issues/139
diff --git a/colander/__init__.py b/colander/__init__.py
index 4104863..ab02e2a 100644
--- a/colander/__init__.py
+++ b/colander/__init__.py
@@ -1635,7 +1635,7 @@ class Time(SchemaType):
 
     This type serializes python ``datetime.time`` objects to a
     `ISO8601 <http://en.wikipedia.org/wiki/ISO_8601>`_ string format.
-    The format includes the date only.
+    The format includes the time only.
 
     The constructor accepts no arguments.
 
@@ -1673,13 +1673,12 @@ class Time(SchemaType):
     err_template =  _('Invalid time')
 
     def serialize(self, node, appstruct):
-        if not appstruct:
-            return null
-
         if isinstance(appstruct, datetime.datetime):
             appstruct = appstruct.time()
 
         if not isinstance(appstruct, datetime.time):
+            if not appstruct:
+                return null
             raise Invalid(node,
                           _('"${val}" is not a time object',
                             mapping={'val':appstruct})
diff --git a/colander/tests/test_colander.py b/colander/tests/test_colander.py
index bf6e6fc..fca4ab5 100644
--- a/colander/tests/test_colander.py
+++ b/colander/tests/test_colander.py
@@ -2257,6 +2257,15 @@ class TestTime(unittest.TestCase):
         expected = time.isoformat().split('.')[0]
         self.assertEqual(result, expected)
 
+    def test_serialize_with_zero_time(self):
+        import datetime
+        typ = self._makeOne()
+        time = datetime.time(0)
+        node = DummySchemaNode(None)
+        result = typ.serialize(node, time)
+        expected = time.isoformat().split('.')[0]
+        self.assertEqual(result, expected)
+
     def test_serialize_with_datetime(self):
         typ = self._makeOne()
         dt = self._dt()