diff --git a/CHANGELOG.md b/CHANGELOG.md
index a841e38d..2250a301 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+## Fixed
+
+- Important bugfix in CFDP PDU header format: The entity length field and the transaction sequence
+  number fields stored the actual length of the field instead of the length minus 1 like specified
+  in the CFDP standard.
+
 ## Changed
 
 - Health functions are virtual now.