  We extend the validity of Kiss's characterization of the commutator from
congruence modular varieties to varieties with a difference term. This fixes a
recently discovered gap in our paper [A finite basis theorem for
difference-term varieties with a finite residual bound, Trans. Amer. Math.
Soc., 368 (2016), 2115--2143]. We also prove some related properties of Kiss
terms in varieties with a difference term.
