diff --git a/processing/post/addSpectralDecomposition.py b/processing/post/addSpectralDecomposition.py
index aa87e6f3c..ba039758a 100755
--- a/processing/post/addSpectralDecomposition.py
+++ b/processing/post/addSpectralDecomposition.py
@@ -78,6 +78,8 @@ for name in filenames:
     for type, data in items.iteritems():
       for column in data['column']:
         (u,v) = np.linalg.eigh(np.array(map(float,table.data[column:column+data['dim']])).reshape(data['shape']))
+        if np.dot(np.cross(v[:,0], v[:,1]), v[:,2]) < 0.0 :
+          v[:, 2] *= -1.0
         table.data_append(list(u))
         table.data_append(list(v.transpose().reshape(data['dim'])))
     outputAlive = table.data_write()                                                                # output processed line