Invalid(Tempered) PrivateKey also authenticates user

SSHCLIENT.connect(host,port);
SSHCLIENT.authPublickey(user, keyLocationArr);

It is okay if I give correct key but should not be working if key is invalid/tempered.
Still it is working and Connected & Authenticated returning TRUE always.

1) Using Correct key and fetching remote file info
2) In next run, changing valid key with invalid/tempered one and still fetching remote file info

Is it BUG in library or any solution you can provide.