Thanks Torsten.��
Indeed, renaming the package solved the problem.

On Thu, Jan 29, 2015 at 12:11 AM, Torsten Bergmann <astares@gmx.de> wrote:
Because "MyPackage" and "MyPackage-Ext" fall into the same
class categories. The name "MyPackage" is part of the string
"MyPackage-Ext".

Packages and class categories are mixed to provide Pharo packages
and with this you are also still able to use old code or
import code from other Smalltalks.

use: "MyPackage-Core" and "MyPackage-Ext" or
�� �� ��"MyPackage-Core" and "MyPackage-Ext-Core"

and you wont have this problem.

If you follow a proper naming scheme (like Seaside and mainly
also Pharo) you wont get this problem.

Bye
T.