diff --git a/lib/bittorrent/swarm/announce.go b/lib/bittorrent/swarm/announce.go
index a236579..b25cdff 100644
--- a/lib/bittorrent/swarm/announce.go
+++ b/lib/bittorrent/swarm/announce.go
@@ -31,6 +31,7 @@ func (a *torrentAnnounce) tryAnnounce(ev tracker.Event) (err error) {
 			PeerID:     a.t.id,
 			Event:      ev,
 			NumWant:    DefaultAnnounceNumWant,
+			Downloaded: a.t.st.DownloadedSize(),
 			Left:       a.t.st.DownloadRemaining(),
 			GetNetwork: a.t.Network,
 		}
diff --git a/lib/storage/fs.go b/lib/storage/fs.go
index ad12557..98bdcb2 100644
--- a/lib/storage/fs.go
+++ b/lib/storage/fs.go
@@ -238,13 +238,26 @@ func (t *fsTorrent) ensureBitfield() {
 	}
 }
 
+func (t *fsTorrent) DownloadedSize() (r uint64) {
+        if t.meta == nil {
+                return
+        }
+        bf := t.Bitfield()
+        r = uint64(bf.CountSet()) * uint64(t.meta.Info.PieceLength)
+        return
+}
+
 func (t *fsTorrent) DownloadRemaining() (r uint64) {
 	if t.meta == nil {
 		return
 	}
 	bf := t.Bitfield()
 	have := uint64(bf.CountSet()) * uint64(t.meta.Info.PieceLength)
-	r = t.meta.TotalSize() - have
+	if have > t.meta.TotalSize() {
+		r = 0
+	} else {
+		r = t.meta.TotalSize() - have
+	}
 	return
 }
 
diff --git a/lib/storage/storage.go b/lib/storage/storage.go
index a12b0d8..d7d679d 100644
--- a/lib/storage/storage.go
+++ b/lib/storage/storage.go
@@ -41,6 +41,9 @@ type Torrent interface {
 	// get bitfield, if cached return cache otherwise compute and cache
 	Bitfield() *bittorrent.Bitfield
 
+	// get number of bytes we already downloaded
+	DownloadedSize() uint64
+
 	// get number of bytes remaining we need to download
 	DownloadRemaining() uint64