diff --git a/desktop/packaging/arch/package-prebuilt.sh b/desktop/packaging/arch/package-prebuilt.sh
index f4ddf1c..4749bed 100755
--- a/desktop/packaging/arch/package-prebuilt.sh
+++ b/desktop/packaging/arch/package-prebuilt.sh
@@ -51,14 +51,17 @@ DEPENDS=(webkit2gtk-4.1 gtk3)
   exit 1
 }
 
-# Single source of truth for the version: the same tauri.conf.json value the
-# .deb and the AppImage are stamped with, so all three artifacts on a release
-# always agree. Plain grep — jq is not guaranteed in the CI image.
+# Single source of truth for the version: the SAME helper the bundle build uses.
+#
+# It used to read tauri.conf.json directly, which was right until dev builds began
+# overriding the version on the command line (M10.9) — the file still says 0.1.0, so
+# the pacman package came out stamped 0.1.0 around a binary reporting 0.1.132. A
+# package that lies about its version is exactly what makes a later "which build is
+# this?" question unanswerable.
 # `|| true` so a miss falls through to the explicit error below rather than
 # aborting on pipefail with no explanation.
-PKGVER="$(grep -oE '"version"[[:space:]]*:[[:space:]]*"[^"]+"' "$SRC_TAURI/tauri.conf.json" |
-  head -1 | sed -E 's/.*"([^"]+)"$/\1/' || true)"
-[ -n "$PKGVER" ] || { echo "ERROR: could not read version from tauri.conf.json" >&2; exit 1; }
+PKGVER="$(sh "$SCRIPT_DIR/../build-version.sh" || true)"
+[ -n "$PKGVER" ] || { echo "ERROR: could not determine the build version" >&2; exit 1; }
 
 # Reproducible-ish: prefer the commit date over "now" so rebuilding the same
 # commit produces the same builddate.