[Numpy-discussion] fill_value in masked arrays

The doc strings for MaskedArray and ma.argsort do not seem consistent. The doc string for MaskedArray says "The fill_value is not used for computation within this module." But the doc string for ma.argsort says "Treating masked values as if they have the value fill_value, return sort indices for sorting along given axis." I'm trying to argsort matrices that have missing values.