Ciao, i work to port some code from Pharo 4.0 to Pharo 6.1-64. My root class into Pharo 4.0 define the properties instance variable and some relative method: a) propertyAt: aKey ifAbsent: aBlock ^ self properties at: aKey ifAbsent: aBlock b) propertyAt: aKey ifAbsentPut: aBlock ^ self properties at: aKey ifAbsentPut: aBlock c) propertyAt: aKey put: aValue ^ self properties at: aKey put: aValue d)...... Now when i port this code into the Pharo 6.1-64 when compile the code the Behavior originalName method implement: ^ (( self isObsolete and:[ self name beginsWith: 'AnObsolete ............ where isObsolete TClass is: self propertyAt: #obsolete ifAbsent: false But my class implement a specific propertyAt: ifAbsent: method and the system generates errors and don't compile the code. Thank you for every consideration. Dario