  The shape function describes (non-perturbative) Fermi motion effects in
semi-inclusive heavy flavour decay. Its renormalization properties are
substantially dependent on the kind of ultraviolet regulator used. For example,
the double logarithm that appears at one loop is larger by a factor 2 in
dimensional regularization than in lattice regularization. We show that
factorization of long-distance effects inside the shape function is achieved
with any regulator considered.
