$OpenBSD: patch-support_sys-mman_c,v 1.2 2014/12/29 10:49:12 robert Exp $
--- support/sys-mman.c.orig	Sun Dec 28 16:27:17 2014
+++ support/sys-mman.c	Sun Dec 28 16:27:25 2014
@@ -17,7 +17,7 @@
 /* For mincore () */
 #define _DARWIN_C_SOURCE
 #endif
-#ifdef __FreeBSD__
+#if defined(__FreeBSD__) || defined(__OpenBSD__)
 /* For mincore () */
 #define __BSD_VISIBLE 1
 #endif
