diff --git a/sbin/hastd/nv.c b/sbin/hastd/nv.c
--- a/sbin/hastd/nv.c
+++ b/sbin/hastd/nv.c
@@ -247,11 +247,8 @@
 			break;
 		}
 		dsize = NVH_DSIZE(nvh);
-		if (dsize == 0) {
-			error = EINVAL;
-			break;
-		}
-		if (size < NVH_SIZE(nvh)) {
+		if (roundup2(dsize, 8) == 0 ||
+		    roundup2(dsize, 8) > size - NVH_HSIZE(nvh)) {
 			error = EINVAL;
 			break;
 		}