client.go     |  5 +++++
 connection.go | 12 ++++++++++++
 misc.go       |  4 ++++

diff --git a/client.go b/client.go
index 76425ccc2c37eb91866848145f685d256df9c586..f8737600b776514a91533fbcce65ee13c90ea839 100644
--- a/client.go
+++ b/client.go
@@ -425,6 +425,11 @@ 				Index: msg.Index,
 				Begin: msg.Begin,
 				Piece: p,
 			})
+		case peer_protocol.Cancel:
+			req := newRequest(msg.Index, msg.Begin, msg.Length)
+			if !conn.PeerCancel(req) {
+				log.Printf("received unexpected cancel: %v", req)
+			}
 		case peer_protocol.Bitfield:
 			if len(msg.Bitfield) < len(torrent.Pieces) {
 				err = errors.New("received invalid bitfield")
diff --git a/connection.go b/connection.go
index ee54f10ccbbc964f256b268b3636a9285696882b..aefe0ba0bb0c26b84e1d6a4bbaf51fd98ae4a0bb 100644
--- a/connection.go
+++ b/connection.go
@@ -88,6 +88,18 @@ 	c.Requests[chunk] = struct{}{}
 	return true
 }
 
+// Returns true if an unsatisfied request was canceled.
+func (c *connection) PeerCancel(r Request) bool {
+	if c.PeerRequests == nil {
+		return false
+	}
+	if _, ok := c.PeerRequests[r]; !ok {
+		return false
+	}
+	delete(c.PeerRequests, r)
+	return true
+}
+
 func (c *connection) Unchoke() {
 	if !c.Choked {
 		return
diff --git a/misc.go b/misc.go
index ce0997f21f6f122f13a8ef977fb498e4bdd2a93c..b0fb349e04024fe7f0d2d08dff820844edd7255e 100644
--- a/misc.go
+++ b/misc.go
@@ -65,6 +65,10 @@ 	Index peer_protocol.Integer
 	chunkSpec
 }
 
+func newRequest(index, begin, length peer_protocol.Integer) Request {
+	return Request{index, chunkSpec{begin, length}}
+}
+
 type pieceByBytesPendingSlice struct {
 	Pending, Indices []peer_protocol.Integer
 }