diff --git a/include/mtp_data.h b/include/mtp_data.h
index 3096cb6..14c2037 100644
--- a/include/mtp_data.h
+++ b/include/mtp_data.h
@@ -39,6 +39,7 @@
 	/* routing info.. */
 	int dpc, opc;
 	int ni;
+	int spare;
 
 	/* internal state */
 	/* the MTP1 link is up */
diff --git a/src/mtp_layer3.c b/src/mtp_layer3.c
index 817b51c..a7afde6 100644
--- a/src/mtp_layer3.c
+++ b/src/mtp_layer3.c
@@ -46,6 +46,7 @@
 	hdr = (struct mtp_level_3_hdr *) msg->l2h;
 	hdr->addr = MTP_ADDR(0x0, link->dpc, link->opc);
 	hdr->ni = link->ni;
+	hdr->spare = link->spare;
 	return msg;
 }