diff --git a/sys/sys/systm.h b/sys/sys/systm.h
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -41,6 +41,7 @@
 #define	_SYS_SYSTM_H_
 
 #include <sys/cdefs.h>
+#include <sys/types.h>
 #include <machine/atomic.h>
 #include <machine/cpufunc.h>
 #include <sys/callout.h>