diff --git a/peer_protocol/protocol.go b/peer_protocol/protocol.go
index bfeb6a0448..2f92ab324d 100644
--- a/peer_protocol/protocol.go
+++ b/peer_protocol/protocol.go
@@ -41,6 +41,11 @@ const (
 
 	// BEP 10
 	Extended MessageType = 20
+
+	// BEP 52
+	HashRequest = 21
+	Hashes      = 22
+	HashReject  = 23
 )
 
 const (
diff --git a/peerconn.go b/peerconn.go
index a1e98b1282..ded9b483e5 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -862,6 +862,8 @@ func (c *PeerConn) mainReadLoop() (err error) {
 			c.updateRequests("PeerConn.mainReadLoop allowed fast")
 		case pp.Extended:
 			err = c.onReadExtendedMsg(msg.ExtendedID, msg.ExtendedPayload)
+		case pp.HashRequest, pp.Hashes, pp.HashReject:
+			err = log.WithLevel(log.Warning, fmt.Errorf("received unimplemented BitTorrent v2 message: %v", msg.Type))
 		default:
 			err = fmt.Errorf("received unknown message type: %#v", msg.Type)
 		}