Hi folks. PackageInfo >> named: aString ^ PackageOrganizer default packageNamed: aString ifAbsent: [(self new packageName: aString) register] creates a new one when it doesn't exist, instead of throwing an error. This has already driven me to different problems difficult to debug. What about doing something like: PackageInfo >> named: aString ifAbsent: aBlock ^ PackageOrganizer default packageNamed: aString ifAbsent: [aBlock value] PackageInfo >> namedForcingNew: aString ^ self named: aString ifAbsent: [(self new packageName: aString) register]. PackageInfo >> named: aString ^ self named: aString ifAbsent: [Error signal: 'The package: ', aString, ' doesnt exist']. The other option is to directly change PackageOrganizer and implement there: PackageOrganizer >> packageNamed: aString ^ packages at: aString ifAbsent: [Error signal: 'The package: ', aString, ' doesnt exist']. With this one the only non confortable is that to use it, is longer...you have to do: PackageOrganizer default packageNamed: 'ZarazaPackage' but it is safer than changing PackageInfo>>named Cheers mariano