Index: lcl/include/custombitmap.inc
===================================================================
--- lcl/include/custombitmap.inc	(revision 15489)
+++ lcl/include/custombitmap.inc	(working copy)
@@ -181,6 +181,10 @@
   UnshareImage(False);
   TSharedCustomBitmap(FSharedImage).FDIB.dsbm.bmWidth := AWidth;
   TSharedCustomBitmap(FSharedImage).FDIB.dsbm.bmHeight := AHeight;
+  RawimageNeeded(True);
+  TSharedCustomBitmap(FSharedImage).FImage.Description.Width := AWidth;
+  TSharedCustomBitmap(FSharedImage).FImage.Description.Height := AHeight;
+  TSharedCustomBitmap(FSharedImage).FImage.CreateData(True);
   Changed(Self);
 end;