diff --git a/lstchain/tools/lstchain_create_irf_files.py b/lstchain/tools/lstchain_create_irf_files.py
index b4fe75e3ef..686f8d8a58 100644
--- a/lstchain/tools/lstchain_create_irf_files.py
+++ b/lstchain/tools/lstchain_create_irf_files.py
@@ -504,7 +504,7 @@ def start(self):
                         'deg'
                     )
             else:
-
+                # add dummy "RAD_MAX" to adapt to 1D analysis with gammapy>0.20.1
                 extra_headers["RAD_MAX"] = (
                     0.1,
                     'deg'