diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 809d8aeccf06a1a3e0eaa26e684f33af262ec324..6c225e57040a4c8161161cd26b9dfd6ca55a2295 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -3,6 +3,11 @@ Unreleased changes
 
 Version 0
 ---------
+0.15.6 / 2020-09-30
+~~~~~~~~~~~~~~~~~~~
+* Fixed the inconsistency of ``len()`` of mapped branches
+  See https://git.km3net.de/km3py/km3io/-/issues/39#note_18429
+
 0.15.5 / 2020-09-30
 ~~~~~~~~~~~~~~~~~~~
 * Fixed a tiny bug in ``km3io.tools.best_track``