diff --git a/draft-ietf-quic-ack-frequency.md b/draft-ietf-quic-ack-frequency.md
index 11ee4124..5d54500e 100644
--- a/draft-ietf-quic-ack-frequency.md
+++ b/draft-ietf-quic-ack-frequency.md
@@ -455,6 +455,10 @@ will wait 'max_ack_delay', increasing the chances of a premature PTO.
 Therefore, if Ignore Order is enabled, the PTO MUST be larger than the peer's
 'max_ack_delay'.
 
+When sending PTO packets, one can include an IMMEDIATE_ACK frame to elicit an
+immediate acknowledgement. This avoids waiting the ack delay for
+acknowledgements of PTO packets, reducing tail latency and allowing the sender
+to exclude the peer's 'max_ack_delay' from subsequent PTO calculations.
 
 # Determining Acknowledgement Frequency {#implementation}