diff --git a/wafo/containers.py b/wafo/containers.py
index 34986a3..cbb38d8 100644
--- a/wafo/containers.py
+++ b/wafo/containers.py
@@ -83,7 +83,7 @@ class PlotData(object):
 
         self.labels = AxisLabels(**kwds)
         if not self.plotter:
-            self.setplotter(kwds.get('plotmethod', None))
+            self.setplotter(kwds.get('plotmethod'))
 
     def copy(self):
         newcopy = empty_copy(self)
@@ -206,7 +206,7 @@ class PlotData(object):
         if axis is None:
             axis = plt.gca()
         tmp = None
-        default_plotflag = self.plot_kwds.get('plotflag', None)
+        default_plotflag = self.plot_kwds.get('plotflag')
         plotflag = kwds.get('plotflag', default_plotflag)
         if not plotflag and self.children is not None:
             axis.hold('on')
diff --git a/wafo/transform/core.py b/wafo/transform/core.py
index fc59814..1595791 100644
--- a/wafo/transform/core.py
+++ b/wafo/transform/core.py
@@ -38,7 +38,7 @@ class TrCommon(object):
     """
 
     def __init__(self, mean=0.0, var=1.0, skew=0.16, kurt=3.04, *args, **kwds):
-        sigma = kwds.get('sigma', None)
+        sigma = kwds.get('sigma')
         if sigma is None:
             sigma = sqrt(var)
         self.mean = mean
@@ -183,8 +183,8 @@ class TrData(PlotData, TrCommon):
         super(TrData, self).__init__(*args, **options)
         self.ymean = kwds.get('ymean', 0e0)
         self.ysigma = kwds.get('ysigma', 1e0)
-        self.mean = kwds.get('mean', None)
-        self.sigma = kwds.get('sigma', None)
+        self.mean = kwds.get('mean')
+        self.sigma = kwds.get('sigma')
 
         if self.mean is None:
             # self.mean = np.mean(self.args)