diff --git a/make_mirror.sh b/make_mirror.sh
index d7fc31a..9d1e777 100755
--- a/make_mirror.sh
+++ b/make_mirror.sh
@@ -539,7 +539,10 @@ END
 		copy-in "$tmpdir/worker.sh" / : \
 		copy-in "$tmpdir/mini-httpd" /etc/default : \
 		copy-in "$tmpdir/hosts" /etc/ : \
-		touch /mmdebstrap-testenv :
+		touch /mmdebstrap-testenv : \
+		sync : \
+		umount / : \
+		shutdown
 	qemu-img convert -O qcow2 "$tmpdir/debian-$DEFAULT_DIST.img" "$newcachedir/debian-$DEFAULT_DIST.qcow"
 	cleanuptmpdir
 	trap "cleanup_newcachedir" EXIT INT TERM
diff --git a/mmdebstrap b/mmdebstrap
index 696a21d..f1a0f68 100755
--- a/mmdebstrap
+++ b/mmdebstrap
@@ -5079,8 +5079,8 @@ Use as replacement for autopkgtest-build-qemu and vmdb2:
         part-set-bootable /dev/sda 1 true : \
         mkfs ext2 /dev/sda1 : mount /dev/sda1 / : \
         tar-in debian-unstable.tar / xattrs:true : \
-        extlinux / : \
-        copy-in extlinux.conf /
+        extlinux / : copy-in extlinux.conf / : \
+        sync : umount / : shutdown
     $ qemu-img convert -O qcow2 debian-unstable.img debian-unstable.qcow2
 
 =end comment