diff --git a/src/uwtools/drivers/chgres_cube.py b/src/uwtools/drivers/chgres_cube.py
index 39cbe921f..2a5f2c2cf 100644
--- a/src/uwtools/drivers/chgres_cube.py
+++ b/src/uwtools/drivers/chgres_cube.py
@@ -59,6 +59,7 @@ def namelist_file(self):
         ] + [
             Path(config_files["data_dir_input_grid"]) / config_files[k]
             for k in ("atm_files_input_grid", "grib2_file_input_grid", "sfc_files_input_grid")
+            if k in config_files
         ]
         base_file = self._driver_config["namelist"].get("base_file")
         yield [file(input_path) for input_path in input_paths] + (