[gentoo-dev] The following USE changes are necessary to proceed - Why?

[Hilco Wijbenga]

Hi all,

I am about to upgrade gnutls. Given the output below:

centaur ~ # emerge gnutls -vp

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  N     ] dev-libs/nettle-2.4  USE="gmp ssl" 1,051 kB
[ebuild     U  ] net-libs/gnutls-2.12.16 [2.10.5] USE="cxx nettle%*
zlib -bindist -doc -examples -guile -lzo -nls -pkcs11% -static-libs%
-test" 7,000 kB

Total: 2 packages (1 upgrade, 1 new), Size of downloads: 8,051 kB

The following USE changes are necessary to proceed:
#required by net-libs/gnutls-2.12.16[nettle], required by gnutls (argument)
>=dev-libs/nettle-2.4 gmp

So I added the nettle USE flag. I tried both package.use and make.conf
but it doesn't seem to make any difference: Portage keeps giving me
the above output.

Why does portage keep complaining? I'm sure that after the update
everything will be fine but it seems to me that Portage should not
tell me about USE changes if I've already made them?

Cheers,
Hilco