anchor.diff:      (error "classes don't agree"))
     (when method-class-p
       (cond ((symbolp method-class)
  -	   (let ((class (sicl-environment:find-class method-class
  -						     environment)))
  +	   (let ((class (sicl-global-environment:find-class
  +			 method-class environment)))
   	     (when (null class)
   	       (error "no such method class ~s" method-class))
   	     (setf method-class class)))
  
positive.code: 	 (error "generic function class must be a class or a name")))
    (when method-class-p
      (cond ((symbolp method-class)
  	   (let ((class (sicl-environment:find-class method-class
  						     environment)))
  	     (when (null class)
  	       (error "no such method class ~s" method-class))
  	     (setf method-class class)))
  
negative.code:      &key
         environment
         (generic-function-class
  	(sicl-global-environment:find-class
  	 'standard-generic-function environment))
         (method-class nil method-class-p)
       &allow-other-keys)
    (declare (ignore function-name))
    (cond ((symbolp generic-function-class)
  	 (let ((class (sicl-global-environment:find-class
  		       generic-function-class environment)))
  	   (when (null class)
  	     (error "no such generic-function-class ~s"
  		    generic-function-class))
  