diff --git a/pybindgen/cppclass.py b/pybindgen/cppclass.py
index c6440b3..c90e682 100644
--- a/pybindgen/cppclass.py
+++ b/pybindgen/cppclass.py
@@ -1368,7 +1368,7 @@ class CppClassParameterBase(Parameter):
     cpp_class = CppClass('dummy') # CppClass instance
     DIRECTIONS = [Parameter.DIRECTION_IN]
 
-    def __init__(self, ctype, name, direction=Parameter.DIRECTION_IN, is_const=False):
+    def __init__(self, ctype, name, direction=Parameter.DIRECTION_IN, is_const=False, default_value=None):
         """
         ctype -- C type, normally 'MyClass*'
         name -- parameter name
@@ -1376,7 +1376,7 @@ class CppClassParameterBase(Parameter):
         if ctype == self.cpp_class.name:
             ctype = self.cpp_class.full_name
         super(CppClassParameterBase, self).__init__(
-            ctype, name, direction, is_const)
+            ctype, name, direction, is_const, default_value)
 
         ## name of the PyFoo * variable used in parameter parsing
         self.py_name = None
@@ -1416,12 +1416,20 @@ class CppClassParameter(CppClassParameterBase):
         else:
             implicit_conversion_sources = self.cpp_class.get_all_implicit_conversions()
             if not implicit_conversion_sources:
-                self.py_name = wrapper.declarations.declare_variable(
-                    self.cpp_class.pystruct+'*', self.name)
-                wrapper.parse_params.add_parameter(
-                    'O!', ['&'+self.cpp_class.pytypestruct, '&'+self.py_name], self.name)
-                wrapper.call_params.append(
-                    '*((%s *) %s)->obj' % (self.cpp_class.pystruct, self.py_name))
+                if self.default_value:
+                    self.py_name = wrapper.declarations.declare_variable(
+                        self.cpp_class.pystruct+'*', self.name, 'NULL')
+                    wrapper.parse_params.add_parameter(
+                        'O!', ['&'+self.cpp_class.pytypestruct, '&'+self.py_name], self.name, optional=True)
+                    wrapper.call_params.append(
+                        '(%s ? (*((%s *) %s)->obj) : %s)' % (self.py_name, self.cpp_class.pystruct, self.py_name, self.default_value))
+                else:
+                    self.py_name = wrapper.declarations.declare_variable(
+                        self.cpp_class.pystruct+'*', self.name)
+                    wrapper.parse_params.add_parameter(
+                        'O!', ['&'+self.cpp_class.pytypestruct, '&'+self.py_name], self.name)
+                    wrapper.call_params.append(
+                        '*((%s *) %s)->obj' % (self.cpp_class.pystruct, self.py_name))
             else:
                 self.py_name = wrapper.declarations.declare_variable(
                     'PyObject*', self.name)