diff --git a/yesod-core/ChangeLog.md b/yesod-core/ChangeLog.md
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@@ -1,5 +1,9 @@
 # ChangeLog for yesod-core
 
+## 1.6.13
+
+* Introduce `maxContentLengthIO`. [issue #1588](https://github.com/yesodweb/yesod/issues/1588) and [PR #1589](https://github.com/yesodweb/yesod/pull/1589)
+
 ## 1.6.12
 
 * Use at most one valid session cookie per request [#1581](https://github.com/yesodweb/yesod/pull/1581)