Can't parse method argument like numbered parameter

[shuujii]

Ruby

$ ruby -e 'def m(_1) _1 end; p m(:m)'
-e:1: warning: `_1' is reserved for numbered parameter; consider another name
:m

mruby

$ mruby -e 'def m(_1) _1 end; p m(:m)'
-e:1:8: warning: numbered parameter in nested block
-e:1:8: syntax error, unexpected tNUMPARAM, expecting ')'
-e:1:8: numbered parameter outside block