diff --git a/CHANGELOG.md b/CHANGELOG.md
index 782fca2..cdff101 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,7 +10,9 @@ list yields a list of all related PRs for each release.
 
 # [unreleased]
 
-# [v3.2.0] to be released
+# [v4.0.0] to be released
+
+`tmtccmd` version: v5.0.0rc0
 
 ## Added
 
@@ -21,6 +23,7 @@ list yields a list of all related PRs for each release.
 ## Fixed
 
 - Fix for PLOC power switching.
+- Bump `tmtccmd` to v5.0.0rc0 for important bugfix in CFDP header.
 
 # [v3.1.1] 2023-04-17
 
diff --git a/pyproject.toml b/pyproject.toml
index c1ef478..a9fb0e1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,7 +29,7 @@ classifiers = [
     "Topic :: Scientific/Engineering"
 ]
 dependencies = [
-	"tmtccmd ~= 4.1",
+	"tmtccmd ~= 5.0.0a0",
 	"python-dateutil ~= 2.8",
 	# tmtccmd @ git+https://github.com/robamu-org/tmtccmd@<gitRev>#egg=tmtccmd
 ]