[Numpy-discussion] Interesting bug with numpy.ma

[Pierre GM]

All,
I've just been pointed to a strange bug in numpy.ma

import numpy as np
import numpy.ma as ma

assert(ma.masked*float(1) is ma.masked)
assert(float(1)*ma.masked is ma.masked)

assert(ma.masked*np.float(1) is ma.masked)
assert(np.float(1)*ma.masked is ma.masked)

assert(ma.masked*np.float_(1) is ma.masked)
assert(np.float_(1)*ma.masked is ma.masked)

The last assertion fails, and I have no idea why. What's the difference 
between assertions 3 and 5 ? FYI, 
ma.masked=ma.MaskedArray(0.,dtype=np.float_,mask=True), and MaskedArray has a 
__array_priority__ of 15.
Implementing a __rmul__ doesn't work either.

Any idea welcome.