SRFI 241 says:

 > If no pattern of any clause is matched, an exception of type
|&assertion-violation| is raised.

But the name of the assertion violation condition type in R6RS is simply
&assertion, not &assertion-violation.

Best wishes

Daphne

(who made the same mistake at one point in the macrological fascicle,
calling the &syntax condition &syntax-violation; it'll be fixed in the
next released draft)