diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 67e0df14ba0f..002aa31b559b 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -2195,7 +2195,10 @@ void ieee80211_free_txskb(struct ieee80211_hw *hw, struct sk_buff *skb);
  * enabling hardware crypto failed. The set_key() call may also return the
  * value 1 to permit this specific key/algorithm to be done in software.
  *
- * When the cmd is %DISABLE_KEY then it must succeed.
+ * When the cmd is %DISABLE_KEY then it must succeed. If RX uses software
+ * PN checking in mac80211, the function must ensure that after returning
+ * no frame decrypted with this key can be handed to mac80211's RX, i.e.
+ * it must do the necessary tasklet/interrupt thread synchronisation.
  *
  * Note that it is permissible to not decrypt a frame even if a key
  * for it has been uploaded to hardware, the stack will not make any
diff --git a/net/mac80211/key.c b/net/mac80211/key.c
index 2e677376c958..53e83704079e 100644
--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -599,6 +599,25 @@ int ieee80211_key_link(struct ieee80211_key *key,
 
 	increment_tailroom_need_count(sdata);
 
+	/* In the case of PTK rekeying without "Extended Key ID for
+	 * Individually Addressed Frames" capability, the key index 0 will
+	 * be reused as the spec then mandates using key index 0 for PTKs.
+	 * In this case, we must not let the following happen:
+	 *  - old key is replaced by new key here
+	 *  - HW-decrypted (with old key) frame is RX-processed, and given
+	 *    the key matching it bumps up the PN for the *new* key
+	 *  - [key gets HW acceleration, but that is now no longer relevant]
+	 *  - practically all future frames are dropped as the new key uses
+	 *    a small PN and all frames are detected as 'replays'
+	 *
+	 * Avoid this by removing the old key from HW acceleration *before*
+	 * linking in the new key.
+	 */
+	if (local->ops->set_key && old_key) {
+		/* XXX - should flush our local->tasklet here...? */
+		ieee80211_key_disable_hw_accel(old_key);
+	}
+
 	ieee80211_key_replace(sdata, sta, pairwise, old_key, key);
 	ieee80211_key_destroy(old_key, true);