diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index fb975dcfc3..535b298778 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Remove meaningless `ActiveSupport::FrozenObjectError`, which was just an alias of `RuntimeError`.
+
+    *Akira Matsuda*
+
 *   Introduce assert_not to replace warty 'assert !foo'.  *Jeremy Kemper*
 
 *   Prevent `Callbacks#set_callback` from setting the same callback twice.