diff --git a/peerconn.go b/peerconn.go
index 7fd819be..7e20ba3b 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -371,15 +371,16 @@ func (cn *Peer) writeStatus(w io.Writer, t *Torrent) {
 	fmt.Fprintf(w, "\n")
 }
 
-func (cn *Peer) close() {
-	if !cn.closed.Set() {
+func (p *Peer) close() {
+	if !p.closed.Set() {
 		return
 	}
-	cn.discardPieceInclination()
-	cn._pieceRequestOrder.Clear()
-	cn.peerImpl.onClose()
-	for _, f := range cn.callbacks.PeerClosed {
-		f(cn)
+	p.discardPieceInclination()
+	p._pieceRequestOrder.Clear()
+	p.peerImpl.onClose()
+	p.t.decPeerPieceAvailability(p)
+	for _, f := range p.callbacks.PeerClosed {
+		f(p)
 	}
 }
 
@@ -764,7 +765,7 @@ func (cn *Peer) discardPieceInclination() {
 	cn.pieceInclination = nil
 }
 
-func (cn *PeerConn) peerPiecesChanged() {
+func (cn *Peer) peerPiecesChanged() {
 	if cn.t.haveInfo() {
 		prioritiesChanged := false
 		for i := pieceIndex(0); i < cn.t.numPieces(); i++ {
@@ -776,7 +777,7 @@ func (cn *PeerConn) peerPiecesChanged() {
 			cn.updateRequests()
 		}
 	}
-	cn.t.maybeDropMutuallyCompletePeer(&cn.Peer)
+	cn.t.maybeDropMutuallyCompletePeer(cn)
 }
 
 func (cn *PeerConn) raisePeerMinPieces(newMin pieceIndex) {
@@ -793,6 +794,9 @@ func (cn *PeerConn) peerSentHave(piece pieceIndex) error {
 		return nil
 	}
 	cn.raisePeerMinPieces(piece + 1)
+	if !cn.peerHasPiece(piece) {
+		cn.t.incPieceAvailability(piece)
+	}
 	cn._peerPieces.Set(bitmap.BitIndex(piece), true)
 	cn.t.maybeDropMutuallyCompletePeer(&cn.Peer)
 	if cn.updatePiecePriority(piece) {
@@ -802,20 +806,27 @@ func (cn *PeerConn) peerSentHave(piece pieceIndex) error {
 }
 
 func (cn *PeerConn) peerSentBitfield(bf []bool) error {
-	cn.peerSentHaveAll = false
 	if len(bf)%8 != 0 {
 		panic("expected bitfield length divisible by 8")
 	}
-	// We know that the last byte means that at most the last 7 bits are
-	// wasted.
+	// We know that the last byte means that at most the last 7 bits are wasted.
 	cn.raisePeerMinPieces(pieceIndex(len(bf) - 7))
 	if cn.t.haveInfo() && len(bf) > int(cn.t.numPieces()) {
 		// Ignore known excess pieces.
 		bf = bf[:cn.t.numPieces()]
 	}
+	pp := cn.newPeerPieces()
+	cn.peerSentHaveAll = false
 	for i, have := range bf {
 		if have {
 			cn.raisePeerMinPieces(pieceIndex(i) + 1)
+			if !pp.Contains(i) {
+				cn.t.incPieceAvailability(i)
+			}
+		} else {
+			if pp.Contains(i) {
+				cn.t.decPieceAvailability(i)
+			}
 		}
 		cn._peerPieces.Set(i, have)
 	}
@@ -823,14 +834,28 @@ func (cn *PeerConn) peerSentBitfield(bf []bool) error {
 	return nil
 }
 
-func (cn *PeerConn) onPeerSentHaveAll() error {
+func (cn *Peer) onPeerHasAllPieces() {
+	t := cn.t
+	if t.haveInfo() {
+		pp := cn.newPeerPieces()
+		for i := range iter.N(t.numPieces()) {
+			if !pp.Contains(i) {
+				t.incPieceAvailability(i)
+			}
+		}
+	}
 	cn.peerSentHaveAll = true
 	cn._peerPieces.Clear()
 	cn.peerPiecesChanged()
+}
+
+func (cn *PeerConn) onPeerSentHaveAll() error {
+	cn.onPeerHasAllPieces()
 	return nil
 }
 
 func (cn *PeerConn) peerSentHaveNone() error {
+	cn.t.decPeerPieceAvailability(&cn.Peer)
 	cn._peerPieces.Clear()
 	cn.peerSentHaveAll = false
 	cn.peerPiecesChanged()
@@ -1613,10 +1638,11 @@ func (cn *Peer) peerMaxRequests() int {
 func (cn *PeerConn) PeerPieces() bitmap.Bitmap {
 	cn.locker().RLock()
 	defer cn.locker().RUnlock()
-	return cn.peerPieces()
+	return cn.newPeerPieces()
 }
 
-func (cn *Peer) peerPieces() bitmap.Bitmap {
+// Returns a new Bitmap that includes bits for all pieces we have.
+func (cn *Peer) newPeerPieces() bitmap.Bitmap {
 	ret := cn._peerPieces.Copy()
 	if cn.peerSentHaveAll {
 		ret.AddRange(0, cn.t.numPieces())
diff --git a/piece.go b/piece.go
index 248832d0..cee6b7d0 100644
--- a/piece.go
+++ b/piece.go
@@ -55,6 +55,7 @@ type Piece struct {
 
 	publicPieceState PieceState
 	priority         piecePriority
+	availability     int64
 
 	// This can be locked when the Client lock is taken, but probably not vice versa.
 	pendingWritesMutex sync.Mutex
diff --git a/request-strategy.go b/request-strategy.go
index e7349aef..9369905b 100644
--- a/request-strategy.go
+++ b/request-strategy.go
@@ -19,7 +19,7 @@ type pieceRequestOrderPiece struct {
 	index        pieceIndex
 	prio         piecePriority
 	partial      bool
-	availability int
+	availability int64
 }
 
 func (me *clientPieceRequestOrder) addPieces(t *Torrent, numPieces pieceIndex) {
@@ -45,12 +45,13 @@ func (me clientPieceRequestOrder) sort() {
 	sort.SliceStable(me.pieces, me.less)
 }
 
-func (me clientPieceRequestOrder) update() {
+func (me *clientPieceRequestOrder) update() {
 	for i := range me.pieces {
 		p := &me.pieces[i]
-		p.prio = p.t.piece(p.index).uncachedPriority()
+		tp := p.t.piece(p.index)
+		p.prio = tp.uncachedPriority()
 		p.partial = p.t.piecePartiallyDownloaded(p.index)
-		p.availability = p.t.pieceAvailability(p.index)
+		p.availability = tp.availability
 	}
 }
 
@@ -61,7 +62,7 @@ func (me clientPieceRequestOrder) less(_i, _j int) bool {
 		int(j.prio), int(i.prio),
 	).Bool(
 		j.partial, i.partial,
-	).Int(
+	).Int64(
 		i.availability, j.availability,
 	).Less()
 }