diff --git a/CHANGELOG_PENDING.md b/CHANGELOG_PENDING.md
index 40fd2644..ac381c80 100644
--- a/CHANGELOG_PENDING.md
+++ b/CHANGELOG_PENDING.md
@@ -14,6 +14,10 @@ BREAKING CHANGES:
 - [crypto] Rename AminoRoute variables to no longer be prefixed by signature type.
 - [config] Replace MaxNumPeers with MaxNumInboundPeers and MaxNumOutboundPeers
 - [node] NewNode now accepts a `*p2p.NodeKey`
+- [abci] \#2159 Update use of `Validator` ala ADR-018:
+    - Remove PubKey from `Validator` and introduce `ValidatorUpdate`
+    - InitChain and EndBlock use ValidatorUpdate
+    - Update field names and types in BeginBlock
 
 FEATURES:
 - [types] allow genesis file to have 0 validators ([#2015](https://github.com/tendermint/tendermint/issues/2015))