diff --git a/makerepropkg.in b/makerepropkg.in
index 51c2dd2..0721f65 100755
--- a/makerepropkg.in
+++ b/makerepropkg.in
@@ -144,6 +144,9 @@ export SOURCE_DATE_EPOCH="${buildinfo[builddate]}"
 PACKAGER="${buildinfo[packager]}"
 BUILDDIR="${buildinfo[builddir]}"
 
+trimprefix=${pkgfile%.pkg.tar*}
+PKGEXT=${pkgfile#$trimprefix}
+
 # nuke and restore reproducible testenv
 for copy in "${buildroot}"/*/; do
     [[ -d ${copy} ]] || continue
@@ -166,7 +169,7 @@ makechrootpkg -r "${buildroot}" -l "${chroot}" -- --packagelist || exit 1
 
 # set detected makepkg.conf options
 {
-    for var in PACKAGER BUILDDIR; do
+    for var in PACKAGER BUILDDIR PKGEXT; do
         printf '%s=%s\n' "${var}" "${!var@Q}"
     done
     printf 'OPTIONS=(%s)\n' "${buildopts[*]@Q}"