--- /usr/portage/eclass/mozextension.eclass     2011-10-27 16:09:09.267746877 +0530
+++ mozextension.eclass 2011-10-27 14:27:24.976498674 +0530
@@ -4,7 +4,7 @@
 #
 # mozextention.eclass: installing firefox extensions and language packs
 
-inherit eutils
+inherit eutils multilib
 
 DEPEND="app-arch/unzip"
 
@@ -50,6 +50,6 @@
        # determine id for extension
        emid="$(sed -n -e '/install-manifest/,$ { /em:id/!d; s/.*[\">]\([^\"<>]*\)[\"<].*/\1/; p; q }' "${x}"/install.rdf)" \
                || die "failed to determine extension id"
-       insinto "${MOZILLA_FIVE_HOME}"/extensions/${emid}
+       insinto /usr/$(get_libdir)/mozilla/extensions/${appid}/${emid}
        doins -r "${x}"/* || die "failed to copy extension"
 }