diff --git a/Gemfile.lock b/Gemfile.lock
index 5eacad2..f0b942c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -12,6 +12,8 @@ GEM
     json (1.8.1)
     multi_json (1.10.1)
     rake (10.3.2)
+    rdoc (4.1.2)
+      json (~> 1.4)
     redcarpet (3.1.2)
     rspec (3.0.0)
       rspec-core (~> 3.0.0)
@@ -38,6 +40,7 @@ PLATFORMS
 
 DEPENDENCIES
   rake
+  rdoc
   redcarpet
   rscons!
   rspec
diff --git a/rscons.gemspec b/rscons.gemspec
index e95d4b4..2de89b7 100644
--- a/rscons.gemspec
+++ b/rscons.gemspec
@@ -24,5 +24,6 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency "rake"
   gem.add_development_dependency "simplecov"
   gem.add_development_dependency "yard"
+  gem.add_development_dependency "rdoc"
   gem.add_development_dependency "redcarpet"
 end