--- m4/open-slash.m4.orig	2020-06-03 23:04:44.000000000 +1000
+++ m4/open-slash.m4	2020-07-31 00:07:16.492646000 +1000
@@ -41,7 +41,7 @@
        [
 changequote(,)dnl
         case "$host_os" in
-          freebsd* | aix* | hpux* | solaris2.[0-9] | solaris2.[0-9].*)
+          bsdsunix* | freebsd* | aix* | hpux* | solaris2.[0-9] | solaris2.[0-9].*)
             gl_cv_func_open_slash="guessing no" ;;
           *)
             gl_cv_func_open_slash="guessing yes" ;;