cmd/tracker-announce/main.go | 6 +++++-
 tracker/http.go              | 1 +

diff --git a/cmd/tracker-announce/main.go b/cmd/tracker-announce/main.go
index a0085de79c5786567828c50e20cad40b20f23709..f6bede88d02db917c3a47271ad6af2821d472730 100644
--- a/cmd/tracker-announce/main.go
+++ b/cmd/tracker-announce/main.go
@@ -30,13 +30,17 @@ }
 
 func main() {
 	flags := struct {
+		Port uint16
 		tagflag.StartPos
 		Torrents []string `arity:"+"`
-	}{}
+	}{
+		Port: 50007,
+	}
 	tagflag.Parse(&flags)
 	ar := tracker.AnnounceRequest{
 		NumWant: -1,
 		Left:    math.MaxUint64,
+		Port:    flags.Port,
 	}
 	var wg sync.WaitGroup
 	for _, arg := range flags.Torrents {
diff --git a/tracker/http.go b/tracker/http.go
index fbe17b694a75eaceb401b6c59159ab6fab5c3085..2d58017998c5d128fdbba0b53c3c171427146a2c 100644
--- a/tracker/http.go
+++ b/tracker/http.go
@@ -69,6 +69,7 @@ 	q := _url.Query()
 
 	q.Set("info_hash", string(ar.InfoHash[:]))
 	q.Set("peer_id", string(ar.PeerId[:]))
+	// AFAICT, port is mandatory, and there's no implied port key.
 	q.Set("port", fmt.Sprintf("%d", ar.Port))
 	q.Set("uploaded", strconv.FormatInt(ar.Uploaded, 10))
 	q.Set("downloaded", strconv.FormatInt(ar.Downloaded, 10))