# File lib/em/deferrable.rb, line 63
63:   def errback &block
64:     return unless block
65:     if @deferred_status == :failed
66:       block.call(*@deferred_args)
67:     elsif @deferred_status != :succeeded
68:       @errbacks ||= []
69:       @errbacks.unshift block # << block
70:     end
71:   end