Can't Enable SRTP in Asterisk menuselect

I worked through the steps found here:
for adding SRTP to the Asterisk 1.8.x builds.
The steps up to and including the srtp library install all gave no errors and completed fine, including the install step.

When I go to build Asterisk using make menu menuselect, the resources line tiem has the following line:
XXX res_srtp
The bottom of the screen says:
Secure RTP (SRTP)
Depends on: srtp(E).

I have searched all menu items and can’t find an option that allows this to be enabled. (So I can’t get it to build with srtp).

Any ideas what I’m doing wrong?
I am running Fedora 11.
I saw no reference to this in the forums.

Did you install libsrtp (and/or associated -dev packages) before running ./configure ?