This Warning is signalled by methods which are deprecated. The use of Object>>#deprecatedExplanation: aString and Object>>#deprecated: aBlock explanation: aString is recommended. Idiom: Imagine I want to deprecate the message #foo. foo ^ 'foo' I can replace it with: foo self deprecatedExplanation: 'The method #foo was not good. Use Bar>>newFoo instead.' ^ 'foo' .... but deprecatedExplanation: aString "This method is OBSOLETE. Use #deprecated: instead." self deprecated: 'Use Object>>deprecated: instead of deprecatedExplanation:.'. Preferences showDeprecationWarnings ifTrue: [Deprecation signal: ('{1} has been deprecated. {2}' translated format: {thisContext sender printString. aString})] and deprecated: aBlock explanation: aString "This method is OBSOLETE. Use #deprecated:block: instead." self deprecated: 'Use Object>>deprecated:block: instead of deprecated:explanation:.'. Preferences showDeprecationWarnings ifTrue: [Deprecation signal: ('{1} has been deprecated. {2}' translated format: {thisContext sender printString. aString})]. ^ aBlock value.