  We investigate a new symmetry of the large deviation function of certain
time-integrated currents in non-equilibrium systems. The symmetry is similar to
the well-known Gallavotti-Cohen-Evans-Morriss-symmetry for the entropy
production, but it concerns a different functional of the stochatic trajectory.
The symmetry can be found in a restricted class of Markov jump processes, where
the network of microscopic transitions has a particular structure and the
transition rates satisfy certain constraints. We provide three physical
examples, where time-integrated observables display such a symmetry. Moreover,
we argue that the origin of the symmetry can be traced back to time-reversal if
stochastic trajectories are grouped appropriately.
