diff --git a/MiRCARTCanvas.py b/MiRCARTCanvas.py
index c62e853..b75af72 100644
--- a/MiRCARTCanvas.py
+++ b/MiRCARTCanvas.py
@@ -181,8 +181,14 @@ class MiRCARTCanvas(wx.Panel):
             self.parentFrame.onCanvasUpdate(size=newCanvasSize, undoLevel=-1)
     # }}}
 
+    # {{{ __del__(self): destructor method
+    def __del__(self):
+        if self.canvasMap != None:
+            self.canvasMap.clear(); self.canvasMap = None;
+    # }}}
+
     #
-    # _init__(self, parent, parentFrame, defaultCanvasPos, defaultCanvasSize, defaultCellSize): initialisation method
+    # __init__(self, parent, parentFrame, defaultCanvasPos, defaultCanvasSize, defaultCellSize): initialisation method
     def __init__(self, parent, parentFrame, defaultCanvasPos, defaultCanvasSize, defaultCellSize):
         super().__init__(parent, pos=defaultCanvasPos,      \
             size=[w*h for w,h in zip(defaultCanvasSize, defaultCellSize)])
diff --git a/MiRCARTCanvasBackend.py b/MiRCARTCanvasBackend.py
index 154b0ca..f7b20e2 100644
--- a/MiRCARTCanvasBackend.py
+++ b/MiRCARTCanvasBackend.py
@@ -141,7 +141,8 @@ class MiRCARTCanvasBackend():
             newBitmap = wx.Bitmap(winSize)
             newDc.SelectObject(newBitmap)
             newDc.Blit(0, 0, *self.canvasBitmap.GetSize(), oldDc, 0, 0)
-            self.canvasBitmap = newBitmap
+            oldDc.SelectObject(wx.NullBitmap)
+            self.canvasBitmap.Destroy(); self.canvasBitmap = newBitmap;
         self.canvasSize = canvasSize; self.cellSize = cellSize;
         self._font = wx.Font(       \
             8,                      \
@@ -166,7 +167,7 @@ class MiRCARTCanvasBackend():
     # }}}
 
     #
-    # _init__(self, canvasSize, cellSize): initialisation method
+    # __init__(self, canvasSize, cellSize): initialisation method
     def __init__(self, canvasSize, cellSize):
         self._initBrushesAndPens()
         self.reset(canvasSize, cellSize)
diff --git a/MiRCARTCanvasJournal.py b/MiRCARTCanvasJournal.py
index d487a60..6bbaa81 100644
--- a/MiRCARTCanvasJournal.py
+++ b/MiRCARTCanvasJournal.py
@@ -68,10 +68,14 @@ class MiRCARTCanvasJournal():
     # }}}
     # {{{ resetCursor(self): XXX
     def resetCursor(self):
+        if self.patchesCursor != None:
+            self.patchesCursor.clear()
         self.patchesCursor = []
     # }}}
     # {{{ resetUndo(self): XXX
     def resetUndo(self):
+        if self.patchesUndo != None:
+            self.patchesUndo.clear()
         self.patchesUndo = [None]; self.patchesUndoLevel = 0;
     # }}}
     # {{{ updateCurrentDeltas(self, undoPatches, redoPatches): XXX
@@ -80,6 +84,11 @@ class MiRCARTCanvasJournal():
         self.patchesUndo[0][1].append(redoPatches)
     # }}}
 
+    # {{{ __del__(self): destructor method
+    def __del__(self):
+        self.resetCursor(); self.resetUndo();
+    # }}}
+
     #
     # __init__(self): initialisation method
     def __init__(self):
diff --git a/MiRCARTFrame.py b/MiRCARTFrame.py
index 3a3d3bf..4c929dc 100644
--- a/MiRCARTFrame.py
+++ b/MiRCARTFrame.py
@@ -227,6 +227,12 @@ class MiRCARTFrame(MiRCARTGeneralFrame):
                 toolBar.EnableTool(self.CID_REDO[0], False)
     # }}}
 
+    # {{{ __del__(self): destructor method
+    def __del__(self):
+        if self.panelCanvas != None:
+            del self.panelCanvas; self.panelCanvas = None;
+    # }}}
+
     #
     # __init__(self, parent, appSize=(840, 630), defaultCanvasPos=(0, 75), defaultCanvasSize=(100, 30), defaultCellSize=(7, 14)): initialisation method
     def __init__(self, parent, appSize=(840, 630), defaultCanvasPos=(0, 75), defaultCanvasSize=(100, 30), defaultCellSize=(7, 14)):