diff --git a/2DTools/2DfilletTool.rb b/2DTools/2DfilletTool.rb
--- a/2DTools/2DfilletTool.rb
+++ b/2DTools/2DfilletTool.rb
@@ -334,6 +334,7 @@
       puts db"No intersection!"
       return nil
     end#if
+    gp1 = nil
     if @alt ### ==chamfer
         e1=@edge1.vertices.sort_by{|i|i.position.distance crosspoint}.reverse[0].position
         ee1=@edge1.vertices.sort_by{|i|i.position.distance crosspoint}.reverse[1].position
@@ -400,7 +401,7 @@
         arcbits=[arcedges[0]];arc_con=arcedges[0].all_connected
         arc_con.each{|e|arcbits<<e if e.valid?}
         gp1=ents.add_group(arcbits)
-        gp2=gp1.copy;gp1.erase!;gp2.explode
+        gp2=gp1.copy;gp2.explode
         ### now tidy loose edges...
         ed1x=ents.add_line(p1,ee1)if e1.distance(p1)<e1.distance(ee1)
         ed2x=ents.add_line(p2,ee2)if e2.distance(p2)<e2.distance(ee2)
@@ -420,6 +421,11 @@
     ###
     view.invalidate
     view.model.commit_operation
+    if(!gp1.nil?)
+        model.start_operation("ShouldntShowupInUndoRedoStack0", true, false, true)
+        gp1.erase!
+        model.commit_operation
+    end
     reset(view)
 end