Many people find out the hard way that their bunny can jump that high. If you already have the 36″ one then you probably will be OK. If you go to buy a new one, or can exchange the 32″, then try to get a 42″ one instead.
Either way, an inexpensive way to prevent it is to make a cover over the top by using a sheet. You want to find a small sheet (like a kid’s twin flat) and stretch it taught across the top. Then get a bunch of clamps at a hardware store or Walmart and clamp it firmly around in several places. Don’t leave gaps big enough for a bunny to worm through. Your bunny may try again but you don’t want him getting stuck or caught (like a paw) and hurting himself.
Some xpens sell a plastic fitted cover separately, so you could do an online search for one from your manufacturer and order it. Usually the most effective is when it’s just too high for the bunny to try again.
You could build a cover made out of thin wood, like balsa, and fit it to the xpen, possibly with a hinge or latch to take it on and off easily. Peruse the xpens and pix in this section for more ideas on habitats.
Does anyone here have a really effective top to their xpen? Please reply with suggestions.