diff --git a/sys/fs/puffs/puffs_vfsops.c b/sys/fs/puffs/puffs_vfsops.c
index 3b54b0dcd5e5..8edf03d0ea4b 100644
--- a/sys/fs/puffs/puffs_vfsops.c
+++ b/sys/fs/puffs/puffs_vfsops.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: puffs_vfsops.c,v 1.90 2010/06/24 13:03:10 hannken Exp $	*/
+/*	$NetBSD: puffs_vfsops.c,v 1.91 2010/07/06 12:05:18 pooka Exp $	*/
 
 /*
  * Copyright (c) 2005, 2006  Antti Kantee.  All Rights Reserved.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: puffs_vfsops.c,v 1.90 2010/06/24 13:03:10 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: puffs_vfsops.c,v 1.91 2010/07/06 12:05:18 pooka Exp $");
 
 #include <sys/param.h>
 #include <sys/mount.h>
@@ -129,6 +129,15 @@ puffs_vfsop_mount(struct mount *mp, const char *path, void *data,
 		goto out;
 	}
 
+	for (i = 0; i < __arraycount(args->pa_spare); i++) {
+		if (args->pa_spare[i] != 0) {
+			printf("puffs_mount: pa_spare[%d] = 0x%x\n",
+			    i, args->pa_spare[i]);
+			error = EINVAL;
+			goto out;
+		}
+	}
+
 	/* use dummy value for passthrough */
 	if (args->pa_fhflags & PUFFS_FHFLAG_PASSTHROUGH)
 		args->pa_fhsize = sizeof(struct fid);