diff --git a/sys/fs/pseudofs/pseudofs_vnops.c b/sys/fs/pseudofs/pseudofs_vnops.c
index 9482db7277a2..347513fc19dc 100644
--- a/sys/fs/pseudofs/pseudofs_vnops.c
+++ b/sys/fs/pseudofs/pseudofs_vnops.c
@@ -515,7 +515,7 @@ pfs_read(struct vop_read_args *va)
 	if (uio->uio_offset < 0 || uio->uio_resid < 0 ||
 	    (offset = uio->uio_offset) != uio->uio_offset ||
 	    (resid = uio->uio_resid) != uio->uio_resid ||
-	    (buflen = offset + resid) < offset || buflen > INT_MAX) {
+	    (buflen = offset + resid + 1) < offset || buflen > INT_MAX) {
 		if (proc != NULL)
 			PRELE(proc);
 		PFS_RETURN (EINVAL);