diff --git a/draft-ietf-quic-transport.md b/draft-ietf-quic-transport.md
index 2f955146f3..034642f117 100644
--- a/draft-ietf-quic-transport.md
+++ b/draft-ietf-quic-transport.md
@@ -1831,7 +1831,9 @@ Connection ID:
 Receivers send ACK frames to inform senders which packets they have received and
 processed, as well as which packets are considered missing.  The ACK frame
 contains between 1 and 256 ACK blocks.  ACK blocks are ranges of acknowledged
-packets.
+packets. Implementations SHOULD NOT generate ACK packets in response to packets
+which only contain ACKs. However, they SHOULD ACK those packets when sending
+ACKs for other packets.
 
 To limit ACK blocks to those that have not yet been received by the sender, the
 receiver SHOULD track which ACK frames have been acknowledged by its peer.  Once