diff --git a/arch/firefox-fourier/PKGBUILD b/arch/firefox-fourier/PKGBUILD
index f6a40514b..53b8a5150 100644
--- a/arch/firefox-fourier/PKGBUILD
+++ b/arch/firefox-fourier/PKGBUILD
@@ -13,7 +13,7 @@
 
 pkgname=firefox-fourier
 pkgver=150.0.1
-pkgrel=4
+pkgrel=5
 pkgdesc='Firefox with V4L2 stateless HW video decode unlocked for mainline Linux Rockchip'
 arch=('aarch64' 'x86_64')
 url='https://www.mozilla.org/firefox'
@@ -171,6 +171,13 @@ LAUNCHER
   # at startup from the package install dir. The 0004 patch covers
   # media.ffmpeg.v4l2-request.enabled; this file covers the three
   # additional prefs that gate the path to the patched code.
+  # Vendor-prefs install path: /usr/lib/firefox-fourier/defaults/preferences/
+  # (Mozilla's canonical scan dir for third-party default-pref drops.) The
+  # browser/defaults/preferences/ alternative looked promising but is NOT a
+  # vendor-prefs scan location in Firefox 150 — empirically confirmed on
+  # fresnel: file shipped there, VAAPI never engaged. Same file under
+  # defaults/preferences/ → MOZ_LOG showed `Requesting pixel format
+  # VAAPI_VLD` + dmabuf surfaces locking end-to-end.
   install -Dm644 "${srcdir}/rockchip-fourier-defaults.js" \
-    "${pkgdir}/usr/lib/firefox-fourier/browser/defaults/preferences/rockchip-fourier-defaults.js"
+    "${pkgdir}/usr/lib/firefox-fourier/defaults/preferences/rockchip-fourier-defaults.js"
 }