Non-Oak signs crash the game instantly when loaded on map.

So when I was making a map of California I put dark oak signs down to represent city locations. So then I got a map and looked at it to see what it looked like. The game instantly crashed. On the crash report, it explains that there is a dark_oak_sign that caused the crash. I then went to another world and placed a spruce sign and looked at the map and sure enough, it crashed. When you load the world again after it crashes, it briefly shows the map and crashes immediately.