diff --git a/RELEASES.md b/RELEASES.md
index 7965d00b8a..87169f6aa1 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,6 +1,8 @@
 Unreleased
 ---------
 
+* `Option` is again a monad. The auxiliary type `OptionM` has been removed. See [Zulip thread](https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/Do.20we.20still.20need.20OptionM.3F/near/279761084).
+
 * Improve `split` tactic. It used to fail on `match` expressions of the form `match h : e with ...` where `e` is not a free variable.
   The failure used to occur during generalization.