Hi, What the subject line says. Here is a test case: CL-USER(1): (use-package :mop) T CL-USER(2): (defclass my-method (standard-method) ()) #<STANDARD-CLASS MY-METHOD {1EE9DE5F}> CL-USER(3): (defclass my-generic-function (standard-generic-function) () (:metaclass funcallable-standard-class) (:default-initargs :method-class (find-class 'my-method))) #<FUNCALLABLE-STANDARD-CLASS MY-GENERIC-FUNCTION {6E06D676}> CL-USER(4): (defgeneric my-function () (:generic-function-class my-generic-function)) #<MY-GENERIC-FUNCTION MY-FUNCTION {2EA1569}> CL-USER(5): (generic-function-method-class #'my-function) #<STANDARD-CLASS STANDARD-METHOD {4E513D61}> The reason is that the defaulting happens in the keyword arguments for ensure-generic-function (in clos.lisp), which thus overrides any default initargs. However, the defaulting should be left to the class. Pascal -- Pascal Costanza