RDEPENDS locking defunct?

[free beastie]

I use PORTSDIR_OVERLAY for a patched version of svgalib (patched upon svgalib-1.4.3-rc4.ebuild) and a self-written ebuild local-pkglock/sgvalib-lock/svgalib-lock-0.1.ebuild:

DESCRIPTION="blabla..."

RDEPEND="=media-libs/svgalib-1.4.3-r4"

which I 'installed' with emerge. As you can see, all this package is supposed to do is introduce a runtime dep to the exact svgalib version. However, when I run

ACCEPT_KEYWORDS="~x86" emerge -p svgalib

(or any package depending upon svgalib), is shows it would replace svgalib with the 1.9.17 version, thus I'd lose my patch. (I do not have "~x86" in my A_C inside make.conf, so adding it should allow exposing whether upgrading will take place)

What am I doing wrong here?