diff --git a/arch/firefox-fourier/mozconfig b/arch/firefox-fourier/mozconfig
index 502853139..cef3f6697 100644
--- a/arch/firefox-fourier/mozconfig
+++ b/arch/firefox-fourier/mozconfig
@@ -34,3 +34,35 @@ ac_add_options --with-distribution-id=de.reauktion.fourier
 
 # Reduce build memory pressure on aarch64 — parallel link is heavy.
 mk_add_options MOZ_PARALLEL_BUILD=8
+
+# Explicit distcc routing. fermi's makepkg.conf has
+# BUILDENV=(distcc ...) which auto-prepends /usr/lib/distcc/bin to
+# $PATH, but mach's configure picks up CC/CXX from the env directly
+# and the distcc wrappers won't fire unless we set them. Mirrors the
+# ffmpeg-v4l2-request-fourier pattern.
+#
+# Note: only the C/C++ portion of the build distributes; rustc and
+# the host-only build steps stay local. Empirically that's still a
+# 30-40% wall-clock win on a 4-worker pool. DISTCC_HOSTS comes from
+# makepkg.conf ('+zeroconf' by default — Avahi-discovers tesla,
+# dcc1, dcc2, ampere).
+if [[ ":${PATH}:" == *":/usr/lib/distcc/bin:"* ]]; then
+    export CC="distcc gcc"
+    export CXX="distcc g++"
+fi
+
+# Explicit distcc routing. fermi's makepkg.conf has
+# BUILDENV=(distcc ...) which auto-prepends /usr/lib/distcc/bin to
+# $PATH, but mach's configure picks up CC/CXX from the env directly
+# and the distcc wrappers won't fire unless we set them. Mirrors the
+# ffmpeg-v4l2-request-fourier pattern.
+#
+# Note: only the C/C++ portion of the build distributes; rustc and
+# the host-only build steps stay local. Empirically that's still a
+# 30-40% wall-clock win on a 4-worker pool. DISTCC_HOSTS comes from
+# makepkg.conf ('+zeroconf' by default — Avahi-discovers tesla,
+# dcc1, dcc2, ampere).
+if [[ ":${PATH}:" == *":/usr/lib/distcc/bin:"* ]]; then
+    export CC="distcc gcc"
+    export CXX="distcc g++"
+fi