diff --git a/src/netif/lowpan6.c b/src/netif/lowpan6.c
index 1793a8af..8479be40 100644
--- a/src/netif/lowpan6.c
+++ b/src/netif/lowpan6.c
@@ -383,6 +383,7 @@ lowpan6_frag(struct netif *netif, struct pbuf *p, const struct lowpan6_link_addr
 #else /* LWIP_6LOWPAN_IPHC */
   /* Send uncompressed IPv6 header with appropriate dispatch byte. */
   lowpan6_header_len = 1;
+  hidden_header_len = 0;
   buffer[ieee_header_len] = 0x41; /* IPv6 dispatch */
 #endif /* LWIP_6LOWPAN_IPHC */