diff --git a/peerconn.go b/peerconn.go
index a2652da9..8933dc77 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -81,7 +81,7 @@ type PeerConn struct {
 	// Chunks that we might reasonably expect to receive from the peer. Due to
 	// latency, buffering, and implementation differences, we may receive
 	// chunks that are no longer in the set of requests actually want.
-	validReceiveChunks map[request]struct{}
+	validReceiveChunks map[request]int
 	// Indexed by metadata piece, set to true if posted and pending a
 	// response.
 	metadataRequests []bool
@@ -501,9 +501,9 @@ func (cn *PeerConn) request(r request, mw messageWriter) bool {
 	}
 	cn.requests[r] = struct{}{}
 	if cn.validReceiveChunks == nil {
-		cn.validReceiveChunks = make(map[request]struct{})
+		cn.validReceiveChunks = make(map[request]int)
 	}
-	cn.validReceiveChunks[r] = struct{}{}
+	cn.validReceiveChunks[r]++
 	cn.t.pendingRequests[r]++
 	cn.t.requestStrategy.hooks().sentRequest(r)
 	cn.updateExpectingChunks()
@@ -987,6 +987,14 @@ func (c *PeerConn) onReadRequest(r request) error {
 	return nil
 }
 
+func runSafeExtraneous(f func()) {
+	if true {
+		go f()
+	} else {
+		f()
+	}
+}
+
 // Processes incoming BitTorrent wire-protocol messages. The client lock is held upon entry and
 // exit. Returning will end the connection.
 func (c *PeerConn) mainReadLoop() (err error) {
@@ -1026,6 +1034,7 @@ func (c *PeerConn) mainReadLoop() (err error) {
 		}
 		messageTypesReceived.Add(msg.Type.String(), 1)
 		if msg.Type.FastExtension() && !c.fastEnabled() {
+			runSafeExtraneous(func() { torrent.Add("fast messages received when extension is disabled", 1) })
 			return fmt.Errorf("received fast extension message (type=%v) but extension is disabled", msg.Type)
 		}
 		switch msg.Type {
@@ -1090,7 +1099,7 @@ func (c *PeerConn) mainReadLoop() (err error) {
 			err = c.peerSentHaveNone()
 		case pp.Reject:
 			c.deleteRequest(newRequestFromMessage(&msg))
-			delete(c.validReceiveChunks, newRequestFromMessage(&msg))
+			c.decExpectedChunkReceive(newRequestFromMessage(&msg))
 		case pp.AllowedFast:
 			torrent.Add("allowed fasts received", 1)
 			log.Fmsg("peer allowed fast: %d", msg.Index).AddValues(c).SetLevel(log.Debug).Log(c.t.logger)
@@ -1107,6 +1116,17 @@ func (c *PeerConn) mainReadLoop() (err error) {
 	}
 }
 
+func (c *PeerConn) decExpectedChunkReceive(r request) {
+	count := c.validReceiveChunks[r]
+	if count == 1 {
+		delete(c.validReceiveChunks, r)
+	} else if count > 1 {
+		c.validReceiveChunks[r] = count - 1
+	} else {
+		panic(r)
+	}
+}
+
 func (c *PeerConn) onReadExtendedMsg(id pp.ExtensionNumber, payload []byte) (err error) {
 	defer func() {
 		// TODO: Should we still do this?
@@ -1196,11 +1216,11 @@ func (c *PeerConn) receiveChunk(msg *pp.Message) error {
 		torrent.Add("chunks received while choking", 1)
 	}
 
-	if _, ok := c.validReceiveChunks[req]; !ok {
+	if c.validReceiveChunks[req] <= 0 {
 		torrent.Add("chunks received unexpected", 1)
 		return errors.New("received unexpected chunk")
 	}
-	delete(c.validReceiveChunks, req)
+	c.decExpectedChunkReceive(req)
 
 	if c.peerChoking && c.peerAllowedFast.Get(int(req.Index)) {
 		torrent.Add("chunks received due to allowed fast", 1)
diff --git a/peerconn_test.go b/peerconn_test.go
index 439f533a..61d74054 100644
--- a/peerconn_test.go
+++ b/peerconn_test.go
@@ -132,7 +132,7 @@ func BenchmarkConnectionMainReadLoop(b *testing.B) {
 			// The chunk must be written to storage everytime, to ensure the
 			// writeSem is unlocked.
 			t.pieces[0]._dirtyChunks.Clear()
-			cn.validReceiveChunks = map[request]struct{}{newRequestFromMessage(&msg): {}}
+			cn.validReceiveChunks = map[request]int{newRequestFromMessage(&msg): 1}
 			cl.unlock()
 			n, err := w.Write(wb)
 			require.NoError(b, err)