reader.go | 2 ++

diff --git a/reader.go b/reader.go
index 12caf4cad06d16c37dcfa1079edd66d4f8ade975..0f92343a20c3b448d8567b8e37a2071836f030a7 100644
--- a/reader.go
+++ b/reader.go
@@ -135,8 +135,10 @@ 		if n != 0 {
 			return
 		}
 		log.Printf("%s: error reading from torrent storage pos=%d: %s", r.t, pos, err)
+		r.t.cl.mu.Lock()
 		r.t.torrent.updatePieceCompletion(pi)
 		r.t.torrent.updatePiecePriority(pi)
+		r.t.cl.mu.Unlock()
 	}
 }