diff --git a/templates/real-from-d2-ana/prepare_namelist.py b/templates/real-from-d2-ana/prepare_namelist.py
index 3ea9988e56e22b6d086b6a377cffa66f16e9d70a..bd69447f702ad8df89e21b9bf290d5d434e02bd1 100644
--- a/templates/real-from-d2-ana/prepare_namelist.py
+++ b/templates/real-from-d2-ana/prepare_namelist.py
@@ -42,7 +42,7 @@ analysis_filename = RUNDIR / f"an_R19B07.{Chunk_START_DATE.strftime('%Y%m%d%H%M'
 analysis_inc_filename = RUNDIR / f"an_R19B07.{Chunk_START_DATE.strftime('%Y%m%d%H%M')}00_inc.{MEMBER[1:]}"
 
 
-boundary_filename = f"latbc_<dddhh>.m{MEMBER[1:]}.grib"
+boundary_filename = f"latbc_<dddhh>.M{MEMBER[1:]}.grib"
 
 # Read custom namelist parameters from configuration
 atmosphere_namelist_string = """