--- a/aaa_base.SlackBuild	2017-09-18 19:15:19.748282651 +0100
+++ b/aaa_base.SlackBuild	2017-09-18 19:16:56.221282697 +0100
@@ -57,9 +57,9 @@
 chmod 644 $PKG/etc/os-release
 
 # Add lib64 directories on x86_64:
-if [ "$ARCH" = "x86_64" ]; then
-  mkdir -p $PKG/lib64 $PKG/usr/lib64 $PKG/usr/local/lib64
-fi
+case "$ARCH" in
+  x86_64|aarch64) mkdir -p $PKG/lib64 $PKG/usr/lib64 $PKG/usr/local/lib64 ;;
+esac
 
 # Build the package:
 cd $PKG