[j-nsp] deleting ntp server from config, perhaps a bug?

[Drew Weaver]

Hello,

I added 0.pool.ntp.org, 1.pool.ntp.org, 2.pool.ntp.org, 3.pool.ntp.org to system ntp on an MX80 running JunOS 15.

[edit system ntp]
drew at charlie# show
server 216.230.228.242;
server 45.79.109.111;
server 172.98.193.44;
server 69.195.159.158;

I need to deactivate/delete a few of these:

[edit system ntp]
drew at charlie# delete server 216.230.228.242
warning: statement not found

drew at charlie# deactivate server 216.230.228.242
warning: statement not found

Is there any way to do this other than simply deleting the entire block and starting over?

Thanks,
-Drew