moar+nativecall+precompilation bug

foo.pm6

module foo;
use NativeCall;
sub zlibVersion() returns Str is encoded("ascii") is native("libz.so.1") is export { * };

terminal output

> perl6 -I. -Mfoo -e 'say zlibVersion'
1.2.8
> perl6 --target=mbc --output=foo.moarvm foo.pm6
> perl6 -I. -Mfoo -e 'say zlibVersion'
Cannot invoke null object
  in sub param_list_for at lib/NativeCall.pm6:42
  in method postcircumfix:<( )> at lib/NativeCall.pm6:113
  in block  at -e:1