diff --git a/configure.ac b/configure.ac
index 898b6ed..ce273dd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -8,6 +8,14 @@ m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 AC_SUBST([USER_CFLAGS], "-O2 $CFLAGS")
 CFLAGS="$CFLAGS -Wall -Werror -std=c99 -g -Wno-pointer-sign -DHAVE_CRYPTODEV -DLIBRESSL_INTERNAL"
 
+case $target_os in
+     *openbsd*)
+     ;;
+     *)
+     CFLAGS=$CFLAGS -D__bounded__(x,y,z)
+     ;;
+esac
+
 case $target_os in
 	*darwin*)
 		TARGET_OS=darwin;