Comment to: "A note on failure of the ladder approximation to QCD" [Phys. Lett. B 640 (2006) 196 ]

In the paper [Hong-Shi Zong, Wei-Min Sun, Phys. Lett. B 640 (2006) 196], the authors claim that our proof of the inconsistency of the ladder approximation to QCD [Phys. Lett. B 611 (2005) 129] was incorrect. However, their claim is based on a derivation which contains a rough mathematical mistake, namely the unjustified change of variables in the divergent (though regularized) integrals. In this comment I will show this explicitly, so our conclusion that the ladder approximation to QCD is inconsistent remains, of course, correct.