peerconn.go | 3 +++

diff --git a/peerconn.go b/peerconn.go
index 4aee30fdbf557f712f5e2fa08c3d51a46a4e92b8..2174b0f620e677c68812abd010b95b3a711b68e4 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -563,6 +563,9 @@ 	}
 	if cn.t.pieceQueuedForHash(pieceIndex(r.Index)) {
 		panic("piece is queued for hash")
 	}
+	if cn.peerChoking && !cn.peerAllowedFast.Contains(bitmap.BitIndex(r.Index)) {
+		panic("peer choking and piece not allowed fast")
+	}
 	return nil
 }