pax -rw choking on 256-byte filename

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I tried to copy a tree with pax -wr -pe that included a 256-byte filename.
I got an error
	pax: cannot create <destination dir>/./<dirs>/<long filename>.mInz1u (File name too long)
Why does pax try to create the destination with a random-looking suffix?