From 52f4c3aef37d4a053cc6d0e26678af360c03d58a Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel.jakob@epfl.ch>
Date: Thu, 3 Mar 2016 14:05:06 +0100
Subject: [PATCH] handle nullptr arguments with custom holder types (fixes
 #124)

---
 include/pybind11/cast.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index a9202f6b7..8547f283a 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -500,10 +500,12 @@ public:
     using type_caster<type>::copy_constructor;
 
     bool load(handle src, bool convert) {
-        if (!src || !typeinfo)
+        if (!src || !typeinfo) {
             return false;
-
-        if (PyType_IsSubtype(Py_TYPE(src.ptr()), typeinfo->type)) {
+        } else if (src.ptr() == Py_None) {
+            value = nullptr;
+            return true;
+        } else if (PyType_IsSubtype(Py_TYPE(src.ptr()), typeinfo->type)) {
             auto inst = (instance<type, holder_type> *) src.ptr();
             value = inst->value;
             holder = inst->holder;