"no such file to load -- spec/rake/spectask" on rake #2

$ rake --trace run
(in /home/egor/foo/rugui/simple_calculator)
rake aborted!
no such file to load -- spec/rake/spectask
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:156:in require' /usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:521:innew_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:156:in require' /usr/lib/ruby/gems/1.8/gems/rugui-1.3.2/lib/rugui/tasks/spec_application.rake:2 /usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:145:inload_without_new_constant_marking'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:145:in load' /usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:521:innew_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:145:in load' /usr/lib/ruby/gems/1.8/gems/rugui-1.3.2/lib/rugui/tasks/rugui.rb:4 /usr/lib/ruby/gems/1.8/gems/rugui-1.3.2/lib/rugui/tasks/rugui.rb:4:ineach'
/usr/lib/ruby/gems/1.8/gems/rugui-1.3.2/lib/rugui/tasks/rugui.rb:4
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:156:in require' /usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:521:innew_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.3/lib/active_support/dependencies.rb:156:in require' /home/egor/foo/rugui/simple_calculator/Rakefile:7 /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2383:inload'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2383:in raw_load_rakefile' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2017:inload_rakefile'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in standard_exception_handling' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2016:inload_rakefile'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2000:in run' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:instandard_exception_handling'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in run' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:31 /usr/bin/rake:19:inload'
/usr/bin/rake:19

rake, version 0.8.7
ruby 1.8.7 (2009-06-12 patchlevel 174) [x86_64-linux]