diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 9b44e9b5499e..b6c1caa90bd5 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -2570,6 +2570,11 @@ getblk(struct vnode * vp, daddr_t blkno, int size, int slpflag, int slptimeo,
 		else
 			bsize = size;
 
+		if (vp->v_bsize != bsize) {
+			printf("WARNING: Wrong block size on vnode: %d should be %d\n", vp->v_bsize, bsize);
+			vprint("Please email phk@FreeBSD.org this info\n", vp);
+		}
+
 		offset = blkno * bsize;
 		vmio = (VOP_GETVOBJECT(vp, NULL) == 0) &&
 		    (vp->v_vflag & VV_OBJBUF);
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index daef020f72e8..a1cfdaa3d2a7 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -841,6 +841,7 @@ getnewvnode(tag, mp, vops, vpp)
 	delmntque(vp);
 	if (mp != NULL)
 		insmntque(vp, mp);
+	vp->v_bsize = mp->mnt_stat.f_iosize;
 
 	return (0);
 }
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 3fc66c4ee913..723e1b0e9847 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -155,6 +155,7 @@ struct vnode {
 #endif
 	dev_t	v_cachedfs;			/* cached fs id */
 	ino_t	v_cachedid;			/* cached file id */
+	int	v_bsize;			/* block size for I/O */
 };
 #define	v_mountedhere	v_un.vu_mountedhere
 #define	v_socket	v_un.vu_socket