Dispatch::Queue.main created with a different Queue class?!?

[ernest.prabhakar@…]

The "Dispatch::Queue.main" fails the equality check in gcd.c, even though it appears identical.

$ macruby -r dispatch -e 'Dispatch::Job.new {sleep 1}.join(Dispatch::Queue.main) {puts "!"}'

/Library/Frameworks/MacRuby.framework/Versions/0.7/usr/lib/ruby/1.9.2/dispatch/job.rb:28:in `join:': expected class of [0x2000c1160] to be Dispatch::Queue [0x20004c8a0], but got Dispatch::Queue [0x2000c1120] (ArgumentError)

from /Users/Shared/MacRuby-trunk/-e:1:in `<main>'

That is, the reported name is the same, but the pointer differs.

Ruby itself seems to think the classes are the same:

$ macruby -r dispatch -e "p Dispatch::Queue.main.class == Dispatch::Queue.concurrent.class" true

Concurrent queues work fine:

$ macruby -r dispatch -e 'Dispatch::Job.new {sleep 1}.join(Dispatch::Queue.concurrent) {puts "!"}'

as do private queues:

$ macruby -r dispatch -e 'Dispatch::Job.new {sleep 1}.join(Dispatch::Queue.new("1")) {puts "!"}'

I don't know if the problems is the class-equality check, or how the main queue gets a class assigned.