diff --git a/kws/bin/plot_det_curve.py b/kws/bin/plot_det_curve.py
index c9036e8..ce1a980 100644
--- a/kws/bin/plot_det_curve.py
+++ b/kws/bin/plot_det_curve.py
@@ -59,7 +59,7 @@ if __name__ == '__main__':
     parser.add_argument(
         '--keywords',
         required=True,
-        help=('keywords, must in the same order as in "dict/words.txt", ' + 
+        help=('keywords, must in the same order as in "dict/words.txt", ' +
               'separated by ", "')
     )
     parser.add_argument('--stats_dir', required=True, help='dir of stats files')