diff --git a/wsme/controller.py b/wsme/controller.py
index f888b4a..b35671d 100644
--- a/wsme/controller.py
+++ b/wsme/controller.py
@@ -230,6 +230,7 @@ class validate(object):
             args = args[1:]
         for i, argname in enumerate(args):
             datatype = self.param_types[i]
+            register_type(datatype)
             mandatory = defaults is None or i < (len(args) - len(defaults))
             default = None
             if not mandatory:
diff --git a/wsme/tests/test_controller.py b/wsme/tests/test_controller.py
index 3383907..9880f4b 100644
--- a/wsme/tests/test_controller.py
+++ b/wsme/tests/test_controller.py
@@ -8,6 +8,7 @@ import webtest
 from wsme import *
 from wsme.controller import getprotocol, scan_api, pexpose
 from wsme.controller import FunctionArgument, FunctionDefinition, CallContext
+from wsme.types import iscomplex
 import wsme.wsgi
 
 
@@ -90,12 +91,20 @@ class TestController(unittest.TestCase):
         assert MyWS.getint._wsme_definition.return_type == int
 
     def test_validate(self):
+        class ComplexType(object):
+            attr = int
+
         class MyWS(object):
             @expose(int)
             @validate(int, int, int)
             def add(self, a, b, c=0):
                 return a + b + c
 
+            @expose(bool)
+            @validate(ComplexType)
+            def setcplx(self, obj):
+                pass
+
         args = MyWS.add._wsme_definition.arguments
 
         assert args[0].name == 'a'
@@ -113,6 +122,8 @@ class TestController(unittest.TestCase):
         assert not args[2].mandatory
         assert args[2].default == 0
 
+        assert iscomplex(ComplexType)
+
     def test_register_protocol(self):
         import wsme.controller
         wsme.controller.register_protocol(DummyProtocol)