diff --git a/RELEASE_NOTES.rst b/RELEASE_NOTES.rst
index 891027c96..33636671c 100644
--- a/RELEASE_NOTES.rst
+++ b/RELEASE_NOTES.rst
@@ -4,6 +4,7 @@ Next release
 All changes
 -----------
 
+- :pull:`704`: Introduce the LPdiag tool for analyzing LP programming problems and related MPS-files.
 - Drop support for Python 3.7, which `reached end-of-life on 2023-06-27 <https://peps.python.org/pep-0537/#lifespan>`__ (:pull:`738`).
   :mod:`message_ix` now requires Python version 3.8 or greater.
 - New reporting operator :func:`.model_periods` and automatic keys ``y::model`` and ``y0`` (:pull:`738`).