diff -wpruN --no-dereference '--exclude=*.orig' a~/plugins/sudoers/auth/pam.c a/plugins/sudoers/auth/pam.c
--- a~/plugins/sudoers/auth/pam.c	1970-01-01 00:00:00
+++ a/plugins/sudoers/auth/pam.c	1970-01-01 00:00:00
@@ -64,7 +64,7 @@
 #include "sudo_auth.h"
 
 /* Only OpenPAM and Linux PAM use const qualifiers. */
-#ifdef PAM_SUN_CODEBASE
+#if defined(PAM_SUN_CODEBASE) && !defined(__illumos__)
 # define PAM_CONST
 #else
 # define PAM_CONST	const