diff --git a/UPGRADE-4.0.md b/UPGRADE-4.0.md
index 49194cae9..fd4dffce7 100644
--- a/UPGRADE-4.0.md
+++ b/UPGRADE-4.0.md
@@ -59,6 +59,7 @@
 - Removed `Dsn::getSecretKey()`.
 - Removed `Dsn::setSecretKey()`.
 - Removed `EventType::default()`.
+- Removed adding the value of the `logger` option as a tag on the event. If you rely on this behaviour, add the tag manually.
 
 - Added return type to `Dsn::getProjectId(): string`.
 - Changed return type to `Options::getLogger(): ?LoggerInterface`.