diff --git a/CHANGELOG.md b/CHANGELOG.md
index 233f3652a..adcac69a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## v0.89
+
+### Fixed
+
+- API could error if multiple alertmanager upstreams belonging to the
+  same cluster were configured, but `cluster` option was unset
+  #3372 (@valihanov).
+
 ## v0.88
 
 ### Added