Hmm... actually I still think it's impossible. If you think about it, that platform is directly above the other platform by 7 tiles. If the stairs go at a 45 degree angle, those stairs should be 14 tiles long. Right now, those stairs are 7 tiles long, which means they're at a 67.5 degree angle. Which is this:
Now because the sprite has an even gap between stairs, the stair tile by default is assumed to be 45 degrees. Which is why it's impossible.
I'm not sure how you'd fit 14 stairs in there (either by extending it from the top or bottom), but if you're ok with the stairs being extremely steep, and some people who notice small things like this having a small problem with depth and perception, then you can leave it the way it is. I'm just a bit stingy when it comes to things like this.
It was actually Liberty that taught me the lesson about stairs being 45 degrees. Theoretically, there should be as many stair tiles as the elevation of the upper platform is above the lower one.