client.go     | 12 ++----------
 connection.go | 26 ++++++++++++++++++++++++++

diff --git a/client.go b/client.go
index 0f7daccb88cfef241adf6eb58c30c5f3c23e933a..8b53a7fd8690f2fc81fb8654051fee71bbe55a8c 100644
--- a/client.go
+++ b/client.go
@@ -1226,10 +1226,7 @@ 			}(),
 		})
 	}
 	if torrent.haveAnyPieces() {
-		conn.Post(pp.Message{
-			Type:     pp.Bitfield,
-			Bitfield: torrent.bitfield(),
-		})
+		conn.Bitfield(torrent.bitfield())
 	} else if me.extensionBytes.SupportsFast() && conn.PeerExtensionBytes.SupportsFast() {
 		conn.Post(pp.Message{
 			Type: pp.HaveNone,
@@ -2660,7 +2657,6 @@ 	}
 	me.pieceChanged(t, int(piece))
 }
 
-// TODO: Check this isn't called more than once for each piece being correct.
 func (me *Client) pieceChanged(t *torrent, piece int) {
 	correct := t.pieceComplete(piece)
 	p := &t.Pieces[piece]
@@ -2684,11 +2680,7 @@ 		}
 	}
 	for _, conn := range t.Conns {
 		if correct {
-			conn.Post(pp.Message{
-				Type:  pp.Have,
-				Index: pp.Integer(piece),
-			})
-			// TODO: Cancel requests for this piece.
+			conn.Have(piece)
 			for r := range conn.Requests {
 				if int(r.Index) == piece {
 					conn.Cancel(r)
diff --git a/connection.go b/connection.go
index 0edda653c6420321fefe40ce31de6fa99849d39d..8f601d5efb811c20f63666503932361ce3e22845 100644
--- a/connection.go
+++ b/connection.go
@@ -64,6 +64,7 @@ 	requestsLowWater int
 	// Indexed by metadata piece, set to true if posted and pending a
 	// response.
 	metadataRequests []bool
+	sentHaves        []bool
 
 	// Stuff controlled by the remote peer.
 	PeerID             [20]byte
@@ -551,3 +552,28 @@ 			return
 		}
 	}
 }
+
+func (cn *connection) Have(piece int) {
+	for piece >= len(cn.sentHaves) {
+		cn.sentHaves = append(cn.sentHaves, false)
+	}
+	if cn.sentHaves[piece] {
+		return
+	}
+	cn.Post(pp.Message{
+		Type:  pp.Have,
+		Index: pp.Integer(piece),
+	})
+	cn.sentHaves[piece] = true
+}
+
+func (cn *connection) Bitfield(haves []bool) {
+	if len(cn.sentHaves) != nil {
+		panic("bitfield must be first have-related message sent")
+	}
+	cn.Post(pp.Message{
+		Type:     pp.Bitfield,
+		Bitfield: haves,
+	})
+	cn.sentHaves = haves
+}