maybe openbsd has schedyield now
diff --git a/include/u.h b/include/u.h
index 1489ebd..68a08a6 100644
--- a/include/u.h
+++ b/include/u.h
@@ -92,6 +92,7 @@
 #	undef _NEEDUINT
 #	undef _NEEDULONG
 #elif defined(__OpenBSD__)
+#	include <sys/types.h>
 #	undef _NEEDUSHORT
 #	undef _NEEDUINT
 #	undef _NEEDULONG