diff --git a/sys/vm/uma.h b/sys/vm/uma.h
index 395415da21db..71027b898cff 100644
--- a/sys/vm/uma.h
+++ b/sys/vm/uma.h
@@ -296,6 +296,7 @@ uma_zone_t uma_zcache_create(char *name, int size, uma_ctor ctor, uma_dtor dtor,
 #define UMA_ALIGN_SHORT	(sizeof(short) - 1)	/* "" short */
 #define UMA_ALIGN_CHAR	(sizeof(char) - 1)	/* "" char */
 #define UMA_ALIGN_CACHE	(0 - 1)			/* Cache line size align */
+#define	UMA_ALIGNOF(type) (_Alignof(type) - 1)	/* Alignment fit for 'type' */
 
 /*
  * Destroys an empty uma zone.  If the zone is not empty uma complains loudly.