diff --git a/eclass/mozconfig-v6.42.eclass b/eclass/mozconfig-v6.42.eclass
index 1feea38..d5caf3f 100644
--- a/eclass/mozconfig-v6.42.eclass
+++ b/eclass/mozconfig-v6.42.eclass
@@ -55,7 +55,7 @@ esac
 # Set the variable to any value if the use flag should exist but not be default-enabled.
 
 # use-flags common among all mozilla ebuilds
-IUSE="${IUSE} dbus debug +gstreamer gstreamer-0 +jemalloc3 neon pulseaudio selinux startup-notification system-cairo system-icu system-jpeg system-sqlite system-libvpx"
+IUSE="${IUSE} dbus debug +gstreamer gstreamer-0 +jemalloc3 neon pulseaudio selinux startup-notification system-cairo system-icu system-jpeg system-sqlite system-libvpx x264"
 
 # some notes on deps:
 # gtk:2 minimum is technically 2.10 but gio support (enabled by default) needs 2.14
@@ -90,7 +90,13 @@ RDEPEND=">=app-text/hunspell-1.2
 	)
 	gstreamer-0? (
 		>=media-libs/gstreamer-0.10.25:0.10
-		media-plugins/gst-plugins-meta:0.10[ffmpeg]
+		|| (
+			x264? ( media-plugins/gst-plugins-meta:0.10[ffmpeg,x264] )
+			!x264? ( media-plugins/gst-plugins-meta:0.10[ffmpeg] )
+		)
+	)
+	!gstreamer-0? (
+		x264? ( virtual/ffmpeg[x264] )
 	)
 	x11-libs/libX11
 	x11-libs/libXcomposite