diff --git a/UPGRADE.md b/UPGRADE.md
index 7e4df9746..bee4e2a04 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -27,6 +27,7 @@ This is a list of backwards compatibility (BC) breaks introduced in ProxyManager
  * Private properties are now also correctly handled by ProxyManager: accessing proxy state via friend classes
    (protected or private scope) does not require any particular workarounds anymore.
  * `ProxyManager\Version::VERSION` was removed. Please use `ProxyManager\Version::getVersion()` instead.
+ * PHP 4 style constructors are no longer supported
 
 # 1.0.0