Ruby error: cannot load such file -- wdm (LoadError)

Question

I've been having some major issues with Jekyll on windows. I finally get it working so i run jekyll build Then jekyll serve --watch Then i get the following error, can anyone help? The full error is: ``` C:/Ruby193/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- wdm (LoadError) from C:/Ruby193/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:i n `require' from C:/Ruby193/lib/ruby/gems/1.9.1/gems/listen-1.3.1/lib/listen/adapter .rb:207:in `load_dependent_adapter' from C:/Ruby193/lib/ruby/gems/1.9.1/gems/listen-1.3.1/lib/listen/adapter s/windows.rb:33:in `load_dependent_adapter' from C:/Ruby193/lib/ruby/gems/1.9.1/gems/listen-1.3.1/lib/listen/adapter .rb:198:in `usable?' from C:/Ruby193/lib/ruby/gems/1.9.1/gems/listen-1.3.1/lib/listen/adapter s/windows.rb:25:in `usable?' from C:/Ruby193/lib/ruby/gems/1.9.1/gems/listen-1.3.1/lib/listen/adapter .rb:190:in `usable_and_works?' from C:/Ruby193/lib/ruby/gems/1.9.1/gems/listen-1.3.1/lib/liste…

Accepted Answer

You seem to be running on a very old version of the `listen` gem (1.3.1). Try to update to latest (2.4.0)

```
$ gem update listen
```

In your `Gemfile`:

```
require 'rbconfig'

gem 'listen', '~> 2.4'
gem 'wdm', '>= 0.1.0' if RbConfig::CONFIG['target_os'] =~ /mswin|mingw|cygwin/i
```

Added the gem wdm since i'm not sure if the listen gem will require it by itself but as the readme states this is optional, otherwise it will fallback to polling which is a less efficient way of doing it.

Ruby error: cannot load such file -- wdm (LoadError)

Solution

Problem