Hello, I am unable to get the simple numpy.ctypeslib.ndpointer docstring example from <http://docs.scipy.org/doc/numpy/reference/routines.ctypeslib.html> working on Windows. Given a DLL `foo.dll` that exports a function `int bar(double *)`, calling foo.bar using the np.ctypeslib.ndpointer approach always fails with a ctypes.ArgumentError: In [5]: foo = ctypes.CDLL('foo.dll') In [6]: foo.bar.argtpes = [np.ctypeslib.ndpointer(dtype=np.float64, ndim=1, flags='C_CONTIGUOUS')] In [7]: a = np.array([1, 2, 3], dtype=np.float64) In [8]: foo.bar(a) ArgumentError: argument 1: <type 'exceptions.TypeError'>: Don't know how to convert parameter 1 This works as expected: In [9]: c_double_p = ctypes.POINTER(ctypes.c_double) In [10]: foo.bar.argtpes = [c_double_p] In [11]: foo.bar(a.ctypes.data_as(c_double_p)) Out[11]: 0 What am I missing? I also tried ndpointer(), several numpy and Python versions, real DLLs, and argument types. A self contained script is attached. Thank you, Christoph