Sore lower back during ab work OK?

I tack on some lying leg raises at the end of my workout a couple days a week. The first set I feel primarily in my abs, but then I feel my lower back being worked significantly in the second and third set. This seems to be the case with almost all ab work I do- when pushing myself, lower back takes over a lot. There is no stabbing pain or anything, just feels like it’s being worked. Significant burn. This seems simple but I wasn’t able to find an answer that was satisfying with search engines, so: is this OK?

It doesn’t matter. Carry on.