--- a/ImageEditor.st	Thu Nov 05 21:14:35 2009 +0100
+++ b/ImageEditor.st	Thu Nov 05 22:56:54 2009 +0100
@@ -4702,14 +4702,15 @@
     oldToNew := ByteArray new:(1 bitShift:depth).
     newColorMap := usedColors asArray.
     newColorMap sort:self sortBlockForColors.
-
-    oldImage colorMap asArray keysAndValuesDo:[:oldIdx :clr |
-        |newPixel|
-
-        (usedColors includes:clr) ifTrue:[
-            newPixel := newColorMap indexOf:clr.
-            oldToNew at:oldIdx put:newPixel-1.
-        ]
+    oldImage colorMap notNil ifTrue:[
+        oldImage colorMap asArray keysAndValuesDo:[:oldIdx :clr |
+            |newPixel|
+
+            (usedColors includes:clr) ifTrue:[
+                newPixel := newColorMap indexOf:clr.
+                oldToNew at:oldIdx put:newPixel-1.
+            ]
+        ].
     ].
 
     oldBits := oldImage bits.