Why does setting ctypes dll.function.restype=c_void_p return long?

It seems odd that even after setting restype, python returns long rather than c_void_p.

For example;

# python code
from ctypes import *
dll = windll.LoadLibrary("my.dll")
dll.my_object_create.restype = c_void_p
x = dll.my_object_create()
print type(x) # prints <type 'long'>

//c++ code
my_object *my_object_create() { return new my_object(); }
void my_object_destroy(my_object *obj) { delete obj; }

I recently had to fix a bug where, feeding x back to another ctypes function, the pointer got trampled. This was fixed by changing the initial dll call to

x = c_void_p(dll.my_object_create())

...I'm guessing somewhere along the line ctypes treated x as 4 bytes long not 8 (64 bit architecture).

So I am wondering if there is a reason why the existing behaviour leads you into this trap?