diff --git a/docs/sources/setup/upgrade/_index.md b/docs/sources/setup/upgrade/_index.md
index e5abde43173d7..547da559bb1fa 100644
--- a/docs/sources/setup/upgrade/_index.md
+++ b/docs/sources/setup/upgrade/_index.md
@@ -36,6 +36,8 @@ The output is incredibly verbose as it shows the entire internal config struct u
 
 ## Main / Unreleased
 
+Loki changes the default value of `-ruler.alertmanager-use-v2` from `false` to `true`. Alertmanager APIv1 was deprecated in Alertmanager 0.16.0 and is removed as of 0.27.0.
+
 ## 3.0.0
 
 {{% admonition type="note" %}}