$ cat test.asm
%define MNSUFFIX
%define MNCURRENT TEST%[MNSUFFIX]
%xdefine var MNCURRENT
$ nasm -v
NASM version 2.15rc0 compiled on Oct 24 2019
$ nasm test.asm
^C
$ oldnasm -v
NASM version 2.14.03rc2 compiled on Aug 31 2019
$ oldnasm test.asm
$