diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index e530f1aab..f0e0e4d42 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,3 +1,8 @@
+# Release v2.2.1
+
+Patch release to explicitly include the **requests** dependency, which was dropped
+from **ixmp4** with release 0.8.1.
+
 # Release v2.2.0
 
 ## Highlights