diff --git a/.travis.yml b/.travis.yml
index 976a9d2..8d33ce3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -35,7 +35,8 @@ before_install:
   - sudo apt-get install gfortran
 # Install packages
 install:
-  - conda install --yes python=$TRAVIS_PYTHON_VERSION numpy scipy pytest matplotlib nose pytest-pep8 pytest-cov mpmath pillow
+  - conda install --yes python=$TRAVIS_PYTHON_VERSION numpy scipy pytest matplotlib nose pytest-pep8 pytest-cov mpmath
+  - pip install pillow
   - pip install numdifftools
   - pip install coveralls
   - pip install codecov
diff --git a/wafo/objects.py b/wafo/objects.py
index bba1a17..d61728d 100644
--- a/wafo/objects.py
+++ b/wafo/objects.py
@@ -91,8 +91,8 @@ class LevelCrossings(PlotData):
         options.update(**kwds)
         super(LevelCrossings, self).__init__(*args, **options)
         self.intensity = kwds.get('intensity', False)
-        self.sigma = kwds.get('sigma', None)
-        self.mean = kwds.get('mean', None)
+        self.sigma = kwds.get('sigma')
+        self.mean = kwds.get('mean')
         # self.setplotter(plotmethod='step')
 
         icmax = self.data.argmax()
@@ -734,7 +734,7 @@ class CyclePairs(PlotData):
         else:
             defnr = kind
 
-        if ((defnr < 0) or (defnr > 3)):
+        if defnr not in [1, 2, 3, 4]:
             raise ValueError('kind must be one of (1,2,3,4).')
 
         m, M = self.get_minima_and_maxima()
@@ -1230,7 +1230,7 @@ class TimeSeries(PlotData):
         dt = self.sampling_period()
 
         yy = self.data.ravel()
-        if not (tr is None):
+        if tr is not None:
             yy = tr.dat2gauss(yy)
         yy = detrend(yy) if hasattr(detrend, '__call__') else yy
         n = len(yy)