diff --git a/build.sh b/build.sh
index 163f89a..a9b1a1f 100755
--- a/build.sh
+++ b/build.sh
@@ -1,4 +1,11 @@
- ./refresh.sh -j && ./mkarchiso.sh
-# sudo rm /var/cache/pacman/pkg/*
+ #!/usr/bin/env bash
+set -euo pipefail
+
+NPROC=$(nproc)
+export MAKEFLAGS="-j${NPROC}"
+export PACMAN_OPTS="--overwrite '*'"
+
+./refresh.sh
+./mkarchiso.sh
 sudo rm -rf ./work
 
diff --git a/mkarchiso.sh b/mkarchiso.sh
index 0cb44a9..7a4da09 100755
--- a/mkarchiso.sh
+++ b/mkarchiso.sh
@@ -1 +1,9 @@
-mkarchiso -L AcreetionOS_XL -v -o ../ISO . -C ./pacman.conf export PACMAN_OPTS="--overwrite '*'" --j$nproc
+#!/usr/bin/env bash
+set -euo pipefail
+
+NPROC=$(nproc)
+export MAKEFLAGS="-j${NPROC}"
+export PACMAN_OPTS="--overwrite '*'"
+export XZ_OPT="-T${NPROC}"
+
+mkarchiso -L AcreetionOS_XL -v -o ../ISO . -C ./pacman.conf