diff --git a/build/arm64.sh b/build/arm64.sh
index 786c715..12d190b 100755
--- a/build/arm64.sh
+++ b/build/arm64.sh
@@ -37,7 +37,9 @@ EOT
 echo "Unmounting second partition"
 sudo umount mnt -R
 
+CORE_COUNT=$((`nproc`-1))
+
 echo "Compressing resulting image"
-xz $RASPIOS_IMG
+xz -T$CORE_COUNT $RASPIOS_IMG
 
 cp $RASPIOS_IMG.xz halis-debian-11.6.0-amd64.img.xz