dumpdev in loader.conf vs rc.d/dumpon

I have recently discovered 'dumpdev' kernel environment variable that is
settable, for example, from loader.conf.  To me it *seems* that this variable
has to be set to a device name / path without the leading '/dev'.  If that's so,
then rc.d/dumpon must prepend '/dev' when passing the value of 'dumpdev' to
dumpon(8).

-- 
Andriy Gapon