  On a normal projective variety the locus of $\mu$-stable bundles that remain
$\mu$-stable on all Galois covers prime to the characteristic is open in the
moduli space of Gieseker semi-stable sheaves. On a smooth projective curve of
genus at least 2 this locus is big in the moduli space of stable bundles, i.e.,
its complement has codimension at least 2.
