I don't think it is actually still true. There was a period when Ukraine was, yes, exporting arms to the Russian Federation because of the natural, long-lasting relationship that had been built up in the Soviet period and continued post-1991. I'm going to defer to Professor Kuzio on this because I know he has studied that subject more than I have, but my recollection is that it is no longer the case.
On October 16th, 2017. See this statement in context.