I got quite confused, why i got error in strange place, the culprit is this one: computeFullBounds [ self doLayoutIn: self layoutBounds ] on: Error do: [ :ex | "This should do it unless you don't screw up the bounds" fullBounds := bounds. ex pass ] used by this: fullBounds "Return the bounding box of the receiver and all its children. Recompute the layout if necessary." fullBounds ifNotNil: [ ^ fullBounds ]. "Errors at this point can be critical so make sure we catch 'em all right" self computeFullBounds. "This should do it unless you don't screw up the bounds" ^ fullBounds So, if error happens, it leaves fullBounds==nil and as result, any code which follows, tries to do something with that nil.. Sure thing it is much more fun figuring out why your morph is broken and where, when such nasty code hides errors. -- Best regards, Igor Stasenko.