diff --git a/packer/qemu/start-vm.sh b/packer/qemu/start-vm.sh
index 2be6917..926b12d 100755
--- a/packer/qemu/start-vm.sh
+++ b/packer/qemu/start-vm.sh
@@ -3,7 +3,7 @@
 set -eu
 export LC_ALL=C
 
-SRC_DIR=$(dirname "$(dirname "$(readlink -f "$0")")")
+SRC_DIR=$(CDPATH='' cd -- "$(dirname -- "${0:?}")" && pwd -P)
 TMP_DIR=$(mktemp -d)
 
 ORIGINAL_DISK=${SRC_DIR:?}/dist/qemu/wireguard.qcow2
@@ -13,7 +13,8 @@ USERDATA_YAML=${SRC_DIR:?}/qemu/http/seed/user-data
 USERDATA_DISK=${TMP_DIR:?}/seed.img
 
 # Remove temporary files on exit
-trap 'rm -rf "${TMP_DIR:?}"; trap - EXIT; exit 0' EXIT TERM INT HUP
+# shellcheck disable=SC2154
+trap 'ret="$?"; rm -rf -- "${TMP_DIR:?}"; trap - EXIT; exit "${ret:?}"' EXIT TERM INT HUP
 
 # Create a snapshot image to preserve the original image
 qemu-img create -b "${ORIGINAL_DISK:?}" -f qcow2 "${SNAPSHOT_DISK:?}"