  We study matching conditions for a spherically symmetric thin shell in
Lovelock gravity which can be read off from the variation of the corresponding
first-order action. In point of fact, the addition of Myers' boundary terms to
the gravitational action eliminates the dependence on the acceleration in this
functional and such that the canonical momentum appears in the surface term in
the variation of the total action. This procedure leads to junction conditions
given by the discontinuity of the canonical momentum defined for an evolution
normal to the boundary. In particular, we correct existing results in the
literature for the thin shell collapse in generic Lovelock theories, which were
mistakenly drawn from an inaccurate analysis of the total derivative terms in
the system.
