mount -v -t nfs4 -o sec=krb5p: mount.nfs4: mount(2): Invalid argument

Issue

• On the NFS client, I try to mount the NFS share:

[root@client ~]# mount -v -t nfs4 -o sec=krb5p nfs.example.org:/ /mnt/ipashare
mount.nfs4: timeout set for Tue Sep 10 16:22:51 2013
mount.nfs4: trying text-based options 'sec=krb5p,addr=10.0.0.1,clientaddr=10.0.0.3'
mount.nfs4: mount(2): Invalid argument
mount.nfs4: an incorrect mount option was specified

While when I use the 'sec=sys' option, this option is accepted.