diff --git a/scripts/deploy_supertuxparty.sh b/scripts/deploy_supertuxparty.sh
index f9d27c6..1cbca22 100755
--- a/scripts/deploy_supertuxparty.sh
+++ b/scripts/deploy_supertuxparty.sh
@@ -23,9 +23,9 @@ fi
 
 # Install Lix
 mkdir -p /opt/supertuxparty
-curl 'https://supertux.party/download/latest/server.zip' > ${TMPDIR:/tmp}/server.zip
-unzip -o -d /opt/supertuxparty ${TMPDIR:/tmp}/server.zip
-rm ${TMPDIR:/tmp}/server.zip
+curl 'https://supertux.party/download/latest/server.zip' > ${TMPDIR:-/tmp}/server.zip
+unzip -o -d /opt/supertuxparty ${TMPDIR:-/tmp}/server.zip
+rm ${TMPDIR:-/tmp}/server.zip
 
 # Create SystemD unit
 cat > /etc/systemd/system/supertuxparty.service <<EOF