diff --git a/acinclude.m4 b/acinclude.m4
index 47df58241..86f1c61f8 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -597,6 +597,22 @@ fi
 AC_MSG_RESULT($ac_cv_type_sig_atomic_t)
 ])
 
+dnl test for mode_t
+
+AC_DEFUN(AC_TYPE_MODE_T,
+[AC_MSG_CHECKING(for mode_t)
+AC_CACHE_VAL(ac_cv_type_mode_t,
+AC_TRY_COMPILE(
+[#include <sys/types.h>],
+[mode_t foo = 1;],
+ac_cv_type_mode_t=yes,
+ac_cv_type_mode_t=no))
+if test "$ac_cv_type_mode_t" = no; then
+	AC_DEFINE(mode_t, unsigned short)dnl
+fi
+AC_MSG_RESULT($ac_cv_type_mode_t)
+])
+
 AC_DEFUN(AC_BROKEN_SNPRINTF, [
 AC_CACHE_CHECK(for working snprintf,ac_cv_func_snprintf_working,
 ac_cv_func_snprintf_working=yes