diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index a7ba0cc..068d8af 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -121,7 +121,7 @@
 	buf[1] = 0;
 	buf[2] = 0;
 	buf[3] = BPDU_TYPE_TCN;
-	br_send_bpdu(p, buf, 7);
+	br_send_bpdu(p, buf, 4);
 }
 
 /*