diff --git a/fsl/fslview/displaycontext/displaycontext.py b/fsl/fslview/displaycontext/displaycontext.py
index 680f75c93a2f36611de3878109d68dfc25d21273..cf527f4735e66b2fa37225aa3d27dd7d41da0993 100644
--- a/fsl/fslview/displaycontext/displaycontext.py
+++ b/fsl/fslview/displaycontext/displaycontext.py
@@ -119,6 +119,8 @@ class DisplayContext(props.SyncableHasProperties):
                 dParent = None
             else:
                 dParent = self.getParent().getDisplay(overlay, overlayType)
+                if overlayType is None:
+                    overlayType = dParent.overlayType
                 
             display = fsldisplay.Display(overlay,
                                          self.__overlayList,
diff --git a/fsl/fslview/views/histogrampanel.py b/fsl/fslview/views/histogrampanel.py
index 92294a5e5398df16dd102946e50b8e6514c3d82e..0eb7a8f9950ddb19201d274aa7f68e96b47ee52d 100644
--- a/fsl/fslview/views/histogrampanel.py
+++ b/fsl/fslview/views/histogrampanel.py
@@ -162,11 +162,8 @@ class HistogramSeries(plotpanel.DataSeries):
 
             self.overlayList.append(self.overlay3D)
 
-            print 'Appended new mask overlay'
             opts = self.displayCtx.getOpts(self.overlay3D, overlayType='mask')
 
-            print 'Got overlay options'
-
             opts.bindProps('volume',    self)
             opts.bindProps('colour',    self)
             opts.bindProps('threshold', self, 'dataRange')
@@ -250,6 +247,7 @@ class HistogramPanel(plotpanel.PlotPanel):
         """De-registers property listeners. """
         plotpanel.PlotPanel.destroy(self)
 
+        self.removeGlobalListener(self._name)
         self._overlayList.removeListener('overlays',        self._name)
         self._displayCtx .removeListener('selectedOverlay', self._name)