diff --git a/src/mog_commons/__init__.py b/src/mog_commons/__init__.py
index 377e1f6..112abf1 100644
--- a/src/mog_commons/__init__.py
+++ b/src/mog_commons/__init__.py
@@ -1 +1 @@
-__version__ = '0.1.13'
+__version__ = '0.1.14'
diff --git a/src/mog_commons/types.py b/src/mog_commons/types.py
index 50840eb..8190473 100644
--- a/src/mog_commons/types.py
+++ b/src/mog_commons/types.py
@@ -12,6 +12,7 @@
 __all__ = [
     'String',
     'Unicode',
+    'Option',
     'ListOf',
     'TupleOf',
     'SetOf',
@@ -101,6 +102,11 @@ def KwArg(cls):
     return DictOf(String, cls)
 
 
+def Option(cls):
+    """Shorthand description for a type allowing NoneType"""
+    return cls + (type(None),) if isinstance(cls, tuple) else (cls, type(None))
+
+
 #
 # Helper functions
 #
@@ -114,7 +120,12 @@ def _get_name(cls):
 
 
 def _check_type(obj, cls):
-    return cls.check(obj) if isinstance(cls, ComposableType) else isinstance(obj, cls)
+    if isinstance(cls, ComposableType):
+        return cls.check(obj)
+    elif isinstance(cls, tuple):
+        return any(_check_type(obj, t) for t in cls)
+    else:
+        return isinstance(obj, cls)
 
 
 #
@@ -147,12 +158,15 @@ def wrapper(*args, **kwargs):
             for arg_name, expect in arg_types.items():
                 assert arg_name in call_args, 'Not found argument: %s' % arg_name
                 actual = call_args[arg_name]
-                assert _check_type(actual, expect), arg_msg % (arg_name, _get_name(expect), type(actual).__name__)
+                if not _check_type(actual, expect):
+                    raise TypeError(arg_msg % (arg_name, _get_name(expect), type(actual).__name__))
 
             ret = func(*args, **kwargs)
             if return_type:
-                assert _check_type(ret, return_type[0]), return_msg % (_get_name(return_type[0]), type(ret).__name__)
+                if not _check_type(ret, return_type[0]):
+                    raise TypeError(return_msg % (_get_name(return_type[0]), type(ret).__name__))
             return ret
+
         return wrapper
 
     return f
diff --git a/tests/mog_commons/test_types.py b/tests/mog_commons/test_types.py
index 67140f3..f2edfc3 100644
--- a/tests/mog_commons/test_types.py
+++ b/tests/mog_commons/test_types.py
@@ -29,6 +29,7 @@ def err_func2():
         @types(bool, int)
         def f():
             pass
+
         return 1
 
     @staticmethod
@@ -36,18 +37,41 @@ def f():
     def predicate():
         return 1
 
+    @types(x=Option((int, float)))
+    def optional_func1(self, x):
+        return x
+
+    @types(int, xs=Option(ListOf(int)))
+    def optional_func2(self, xs=None):
+        return len(xs or [])
+
+    class Foo(object):
+        pass
+
     def test_types(self):
         str_type = '(basestring|str)' if six.PY2 else '(str|bytes)'
 
         self.assertEqual(self.bin_func(10, 20), 30)
-        self.assertRaisesMessage(AssertionError, 'x must be int, not dict.', self.bin_func, {}, 20)
-        self.assertRaisesMessage(AssertionError, 'y must be int, not list.', self.bin_func, 10, [])
+        self.assertRaisesMessage(TypeError, 'x must be int, not dict.', self.bin_func, {}, 20)
+        self.assertRaisesMessage(TypeError, 'y must be int, not list.', self.bin_func, 10, [])
 
         self.assertEqual(self.complex_func(123, [1, 2], 10, 'abc', 'def', [{'x': set([3, 4, 5])}]), 1)
-        self.assertRaisesMessage(AssertionError, 'kw must be dict(%s->float), not dict.' % str_type,
+        self.assertRaisesMessage(TypeError, 'kw must be dict(%s->float), not dict.' % str_type,
                                  self.complex_func, 123, [1, 2], 10, 'abc', 'def', [{'x': set([3, 4, 5])}], x='12.3')
 
-        self.assertRaisesMessage(AssertionError, 'must return bool, not int.', self.predicate)
+        self.assertRaisesMessage(TypeError, 'must return bool, not int.', self.predicate)
+
+        self.assertEqual(self.optional_func1(None), None)
+        self.assertEqual(self.optional_func1(123), 123)
+        self.assertEqual(self.optional_func1(1.23), 1.23)
+        self.assertRaisesMessage(TypeError, 'x must be (int|float|NoneType), not Foo.',
+                                 self.optional_func1, self.Foo())
+
+        self.assertEqual(self.optional_func2(), 0)
+        self.assertEqual(self.optional_func2(None), 0)
+        self.assertEqual(self.optional_func2([1, 2, 3]), 3)
+        self.assertRaisesMessage(TypeError, 'xs must be (list(int)|NoneType), not list.',
+                                 self.optional_func2, [1, 2, 3.4])
 
     def test_types_error(self):
         self.assertRaisesMessage(AssertionError, 'Not found argument: a', self.err_func1, 123)