diff --git a/CHANGELOG.md b/CHANGELOG.md
index 17d6a02..5929c61 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## 0.13.1 - 2023-12-29
+- Upgrade libampl to 2.3.7-20231229.
 - Upgrade ampltools to 0.7.2 adding amplpy.bundle command.
 - Fix issue with environment variables on Windows in a generic way.
 - Add return_output and solvername_options arguments to AMPL.solve