diff --git a/ndbuf.c b/ndbuf.c
index 6c0f339..89ac862 100644
--- a/ndbuf.c
+++ b/ndbuf.c
@@ -78,7 +78,8 @@ ndbuf_t *ndbuf_new_frombuf(char *buf, size_t buf_len, void (*freebuf)(char *))
 
   /* init buffer */
   b->raw = buf;
-  b->rlength = b->ulength = buf_len;
+  b->rlength = buf_len;
+  b->ulength = 0; /* assume it's not used */
   b->flags = b->curr = 0;
   b->freebuf = freebuf;
   b->flags |= NDBUF_NREA;