Comment #1 on issue 3402 by stephane.ducasse: SmalltalkEditor new raises an Error http://code.google.com/p/pharo/issues/detail?id=3402 The #changeParagraph: is bogus: changeParagraph: aParagraph "Install aParagraph as the one to be edited by the receiver." self resetState TextEditor>>paragraph is following: paragraph ^ morph ifNotNil: [morph paragraph] I changed the TextEditor, for creating and initializing it not like: TextEditor new but like: TextEditor newForMorph: morph in that way, TextEditor>>paragraph always works. And for same reason, i removed the #changeParagraph: , because it useless. Also, the following test is now should be rewritten: CompilerEvaluationTest>>testEvaluationOfSelfSend SmalltalkEditorTest >> testCompilationOfUndefinedVar they using old SmalltalkEditor new, instead of (newForMorph:) as well as using #changeParagraph: So, creating SmalltalkEditor can be done like: morph := NewTextMorph new. morph paragraph: paragraph. editor := SmalltalkEditor newForMorph: morph.