diff --git a/src/log_plotter/datalogger_plotter_with_pyqtgraph.py b/src/log_plotter/datalogger_plotter_with_pyqtgraph.py
index 60eed45..09280bb 100755
--- a/src/log_plotter/datalogger_plotter_with_pyqtgraph.py
+++ b/src/log_plotter/datalogger_plotter_with_pyqtgraph.py
@@ -19,7 +19,7 @@
 
 
 class LogPlotter(object):
-    def __init__(self, fname, plot_conf_name, layout_conf_name, title):
+    def __init__(self, fname, plot_conf_name, layout_conf_name, title=None):
         '''
         :param str fname: file name of log
         :param str plot_conf_name: plot yaml file name