diff --git a/UPGRADE-3.4.md b/UPGRADE-3.4.md
index 0119ca02f5..b3058828ce 100644
--- a/UPGRADE-3.4.md
+++ b/UPGRADE-3.4.md
@@ -4,7 +4,7 @@ UPGRADE FROM 3.3 to 3.4
 Config
 ------
 
- * Using protected builder property of TreeBuilder is deprecated and property will be removed in 4.0.
+ * The protected `TreeBuilder::$builder` property is deprecated and will be removed in 4.0.
 
 DependencyInjection
 -------------------
diff --git a/UPGRADE-4.0.md b/UPGRADE-4.0.md
index 4132d06ab6..e4aec37090 100644
--- a/UPGRADE-4.0.md
+++ b/UPGRADE-4.0.md
@@ -6,6 +6,11 @@ ClassLoader
 
  * The component has been removed. Use Composer instead.
 
+Config
+------
+
+ * The protected `TreeBuilder::$builder` property has been removed.
+
 Console
 -------