From 7e28fa1c4ecf0cc7430cd0516090f1942c224ed4 Mon Sep 17 00:00:00 2001
From: Tommaso Tedeschi <tedesk95@gmail.com>
Date: Thu, 28 May 2026 15:53:01 +0200
Subject: [PATCH] Set ownership for TLegend header in cmsstyle.py

Prevent Python garbage collection from deleting TLegend header.
---
 src/cmsstyle/cmsstyle.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/cmsstyle/cmsstyle.py b/src/cmsstyle/cmsstyle.py
index 5094fe2..ca64c9b 100644
--- a/src/cmsstyle/cmsstyle.py
+++ b/src/cmsstyle/cmsstyle.py
@@ -1316,6 +1316,9 @@ def cmsHeader(
         leg.GetListOfPrimitives().AddAt(header, 0)
     else:
         leg.GetListOfPrimitives().AddLast(header)
+    # ROOT >= 6.40 no longer drops Python ownership automatically for this case.
+    # The entry is stored in the TLegend primitive list, so avoid Python GC deleting it.
+    rt.SetOwnership(header, False)
 
 
 # ########  ########     ###    ##      ##