diff --git a/m4/ax_cflags_warn_all.m4 b/m4/ax_cflags_warn_all.m4
index 9235a18c..2e80ed86 100644
--- a/m4/ax_cflags_warn_all.m4
+++ b/m4/ax_cflags_warn_all.m4
@@ -51,7 +51,7 @@
 #
 #   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
 #   Copyright (c) 2010 Rhys Ulerich <rhys.ulerich@gmail.com>
-#   Copyright (c) 2018 John Zaitseff <J.Zaitseff@zap.org.au>
+#   Copyright (c) 2018-24 John Zaitseff <J.Zaitseff@zap.org.au>
 #
 #   This program is free software; you can redistribute it and/or modify it
 #   under the terms of the GNU General Public License as published by the
@@ -79,7 +79,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 25
+#serial 26
 
 AC_DEFUN([AX_FLAGS_WARN_ALL], [
     AX_REQUIRE_DEFINED([AX_PREPEND_FLAG])dnl
@@ -102,6 +102,7 @@ AC_DEFUN([AX_FLAGS_WARN_ALL], [
 	    [fujitsu],		[],
 	    [sdcc],		[],
 	    [sx],		[VAR="-pvctl[,]fullmsg"],
+	    [nvhpc],		[VAR="-Wall"],
 	    [portland],		[],
 	    [gnu],		[VAR="-Wall"],
 	    [sun],		[VAR="-v"],