Got error 404 when access merge_requests api

Created by: wolfg1969

Below are errors found in production.log. The merge_requests web page is ok and I'm sure there are open and closed MRs of my project. The Gitlab version is 6.1 stable.

ActionController::RoutingError (No route matches [GET] "/api/v3/projects/12/merge_requests"):
  vendor/bundle/ruby/2.0.0/gems/actionpack-3.2.13/lib/action_dispatch/middleware/debug_exceptions.rb:21:in `call'
  vendor/bundle/ruby/2.0.0/gems/actionpack-3.2.13/lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
  vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/rack/logger.rb:32:in `call_app'
  vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/rack/logger.rb:16:in `block in call'
  vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/tagged_logging.rb:22:in `tagged'
  vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/rack/logger.rb:16:in `call'
  vendor/bundle/ruby/2.0.0/gems/actionpack-3.2.13/lib/action_dispatch/middleware/request_id.rb:22:in `call'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/methodoverride.rb:21:in `call'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/runtime.rb:17:in `call'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/lock.rb:15:in `call'
  vendor/bundle/ruby/2.0.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:136:in `forward'
  vendor/bundle/ruby/2.0.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:245:in `fetch'
  vendor/bundle/ruby/2.0.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:185:in `lookup'
  vendor/bundle/ruby/2.0.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:66:in `call!'
  vendor/bundle/ruby/2.0.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:51:in `call'
  vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/engine.rb:479:in `call'
  vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/application.rb:223:in `call'
  vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/railtie/configurable.rb:30:in `method_missing'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/builder.rb:134:in `call'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/urlmap.rb:64:in `block in call'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/urlmap.rb:49:in `each'
  vendor/bundle/ruby/2.0.0/gems/rack-1.4.5/lib/rack/urlmap.rb:49:in `call'
  vendor/bundle/ruby/2.0.0/gems/unicorn-4.6.3/lib/unicorn/http_server.rb:552:in `process_client'
  vendor/bundle/ruby/2.0.0/gems/unicorn-4.6.3/lib/unicorn/http_server.rb:632:in `worker_loop'
  vendor/bundle/ruby/2.0.0/gems/unicorn-4.6.3/lib/unicorn/http_server.rb:500:in `spawn_missing_workers'
  vendor/bundle/ruby/2.0.0/gems/unicorn-4.6.3/lib/unicorn/http_server.rb:142:in `start'
  vendor/bundle/ruby/2.0.0/gems/unicorn-4.6.3/bin/unicorn_rails:209:in `<top (required)>'
  vendor/bundle/ruby/2.0.0/bin/unicorn_rails:23:in `load'
  vendor/bundle/ruby/2.0.0/bin/unicorn_rails:23:in `<main>'