Contradiction between the MOP and the standard ?

Hi,

In the CLHS page for ENSURE-GENERIC-FUNCTION, there is this paragraph:

"If function-name specifies a generic function that has a different value for the :generic-function-class argument and if the new generic function class is compatible[1] with the old, change-class is called to change the class of the generic function; otherwise an error is signaled."

In the AMOP however, one can read the following.

From the page on ENSURE-GENERIC-FUNCTION:

"The behavior of this function is actually implemented by the generic function ensure-generic-function-using-class. When ensure-generic-function is called, it immediately calls ensure-generic-function-using-class and returns that result as its own."

And then from the page on ENSURE-GENERIC-FUNCTION-USING-CLASS: "If the class of the generic-function-or-nil argument is not the same as the class specified by the :generic-function-class argument, an error is signaled."

Let alone the fact that this should only apply when there actually is an existing generic function, this seems to be in contradiction with the Common Lisp standard, as it would explicitly forbid changing the class of the generic function, even in a "compatible" way.

Comments?

Footnotes: [1] BTW, what does "compatible" mean ?