I did the exact same thing and was very disappointed that it didn't work.
5KZnsvrXDcP7JFD7GCuZvifrbcBtK4kAe8nHx6ibktgvPJxs4Lp is wrong though. This is the correct one albeit still not the answer:
5KZnsvrXDcP7JFD7GCuZvifrbEBtK4kAe8nHx6ibktgvPJxs4Lp

You are wrong Gatekeeper. For reference the reason why it does get imported is here:
http://gobittest.appspot.com/PrivateKey
play around with it a bit.