diff --git a/Gemfile b/Gemfile
index 10096db..41bf16a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -32,7 +32,7 @@ gem 'turbolinks'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem 'jbuilder', '~> 2.0'
 # bundle exec rake doc:rails generates the API under doc/api.
-gem 'sdoc', '~> 2.3.2', group: :doc
+gem 'sdoc', '~> 2.4.0', group: :doc
 
 # Use ActiveModel has_secure_password
 gem 'bcrypt', '~> 3.1.7'