diff --git a/templates/real-from-dwd-ana/prepare_namelist.py b/templates/real-from-dwd-ana/prepare_namelist.py
index a9be67bc20e08d94b6a08fbc1430e632221ed184..f259ad58d8a9d338b12e75668f9684ff5371d512 100644
--- a/templates/real-from-dwd-ana/prepare_namelist.py
+++ b/templates/real-from-dwd-ana/prepare_namelist.py
@@ -120,7 +120,7 @@ def main():
     """
     # Process atmosphere namelist
     atmosphere_namelist = f90nml.read(ATMOSPHERE_NAMELIST_PATH.as_posix())
-    # Convert output_nml to a cogroup.
+    # Convert output_nml to a co-group.
     atmosphere_namelist.create_cogroup("output_nml")
     print("Original atmosphere namelist:")
     print(atmosphere_namelist)
diff --git a/templates/real-from-ideal/prepare_ideal_namelist.py b/templates/real-from-ideal/prepare_ideal_namelist.py
index af95b8ad9bddaf85f709ce170f7ecc55fdded1cc..b2cafe8334c322a661e8a26d50f0ace41d195783 100644
--- a/templates/real-from-ideal/prepare_ideal_namelist.py
+++ b/templates/real-from-ideal/prepare_ideal_namelist.py
@@ -111,6 +111,8 @@ def main():
     """
     # Process atmosphere namelist
     atmosphere_namelist = f90nml.read(ATMOSPHERE_NAMELIST_PATH.as_posix())
+    # Convert output_nml to a co-group.
+    atmosphere_namelist.create_cogroup("output_nml")
     print("Original atmosphere namelist:")
     print(atmosphere_namelist)
     atmosphere_namelist.patch(atmosphere_namelist_replacements)
diff --git a/templates/real-from-ideal/prepare_namelist.py b/templates/real-from-ideal/prepare_namelist.py
index d377e56ab27d863be6d0bbe3efd9185b62bade2d..fa2d0e7e1db79c1f374e33da1247bfb97ea0cb67 100644
--- a/templates/real-from-ideal/prepare_namelist.py
+++ b/templates/real-from-ideal/prepare_namelist.py
@@ -125,6 +125,8 @@ def main():
 
     # Read custom namelist parameters from configuration file
     atmosphere_custom_namelist = read_namelist(atmosphere_namelist_string)
+    # Convert output_nml to a co-group.
+    atmosphere_namelist.create_cogroup("output_nml")
 
     if atmosphere_custom_namelist is not None:
         try: