Difficulty filling up buckets

I did this at a lava pool, but you can do it everywhere it seems. You have to right click at the bottom of the block, or else you cant fill it properly. If you try filling th It is pretty annoying when trying to do something with lava blocks, so I thought I'd leave it here. If you don't understand what I'm saying, just get an empty bucket in creative and try filling it in a lava pool.