  We study the extended hydrodynamics proposed by Philip Rosenau [Phys. Rev. A
40, 7193 (1989)] in the context of a regularization of the Chapman-Enskog
expansion. We are able to prove that shock waves appear in finite time in
Rosenau's extended Burgers' equation, and we discuss the physical implications
of this fact and its connection with a possible extension of hydrodynamics to
the short wavelength domain.
