diff --git a/ObservationSim/_util.py b/ObservationSim/_util.py
index 16cf2c4c9ff0f540bca7393c46bd83841a0628da..cc2b039005a900c4e1c08de586c0c5d58e3191a8 100755
--- a/ObservationSim/_util.py
+++ b/ObservationSim/_util.py
@@ -13,7 +13,7 @@ def parse_args():
     '''
     parser = argparse.ArgumentParser()
     parser.add_argument('config_file', help='.yaml config file for simulation settings.')
-    parser.add_argument('-c', '--config_dir', help='Directory that houses the ,yaml config file.')
+    parser.add_argument('-c', '--config_dir', help='Directory that houses the .yaml config file.')
     parser.add_argument('-d', '--data_dir', help='Directory that houses the input data.')
     parser.add_argument('-w', '--work_dir', help='The path for output.')
     return parser.parse_args()