According to 7.6.7 [expr.shift] paragraph 2,

The value of E1 << E2 is E1 (interpreted as a bit pattern) left-shifted E2 bit positions; vacated bits are zero-filled. If E1 has an unsigned type, the value of the result is E1 multiplied by the quantity 2 raised to the power E2, reduced modulo ULLONG_MAX+1 if E1 has type unsigned long long int, ULONG_MAX+1 if E1 has type unsigned long int, UINT_MAX+1 otherwise.

This specification does not allow for extended types with rank greater than long long; in particular, it says that the value of a shifted unsigned extended type is truncated as if it were the same width as an unsigned int.

It's unclear that the second sentence has any normative value; it might be better to relegate it to a note or omit it than to correct it.