knife cookbook site vendor fails to extract due to incorrect cwd

$ knife cookbook site vendor zsh
INFO: Downloading zsh from the cookbooks site at version 0.7.0
INFO: Cookbook saved: ./cookbooks/zsh.tar.gz
INFO: Checking out the master branch.
INFO: Checking the status of the vendor branch.
INFO: Creating vendor branch.
INFO: Removing pre-existing version.
INFO: Uncompressing zsh version 0.7.0.
/usr/lib/ruby/gems/1.8/gems/chef-0.8.16/lib/chef/mixin/command.rb:181:in `handle_command_failures': tar zxvf ./cookbooks/zsh.tar.gz returned 2, expected 0 (Chef::Exceptions::Exec)
	from /usr/lib/ruby/gems/1.8/gems/chef-0.8.16/lib/chef/mixin/command.rb:124:in `run_command'
	from /usr/lib/ruby/gems/1.8/gems/chef-0.8.16/lib/chef/knife/cookbook_site_vendor.rb:59:in `run'
	from /usr/lib/ruby/gems/1.8/gems/chef-0.8.16/lib/chef/application/knife.rb:116:in `run'
	from /usr/lib/ruby/gems/1.8/gems/chef-0.8.16/bin/knife:25
	from /usr/bin/knife:19:in `load'
	from /usr/bin/knife:19