diff --git a/misc/PlotCanvas.py b/misc/PlotCanvas.py
index 52eec484e319cef0079f6ad2280d87fa4226620c..3b9eb2b9505caa4ae53d8e841a85363c4f173257 100644
--- a/misc/PlotCanvas.py
+++ b/misc/PlotCanvas.py
@@ -321,6 +321,11 @@ class PlotCanvas(FigureCanvas):
         
             self.nextmask.set_data((self.nextplotmask % 10 +1 )*(self.nextplotmask != 0))
             self.ax3.draw_artist(self.nextmask)
+            
+        else:
+            self.currmask.set_data(np.zeros(self.plotmask.shape))
+            self.previousmask.set_data(np.zeros(self.plotmask.shape))
+            self.nextmask.set_data(np.zeros(self.plotmask.shape))
         
         # Plot cell numbers
         self.ShowCellNumbers()