  We propose a simple model to study the Gouy phase effect in the triple-slit
experiment in which we consider a non-classical path. The Gouy phase differs
for classical or non-classical paths as it depends on the propagation time. In
this case the Gouy phase difference changes the Sorkin parameter $\kappa$ used
to estimate non-classical path contribution in a nontrivial way shedding some
light in the implementation of experiments to detect non-classical path
contributions.
