diff --git a/ruby/Gemfile b/ruby/Gemfile
index c7e97d6b0809901253dac885029b953726e54dcd..33e7e1228c03bedcdaedd9a7f756123014d2993d 100644
--- a/ruby/Gemfile
+++ b/ruby/Gemfile
@@ -3,6 +3,7 @@ source 'https://rubygems.org'
 gem 'github-linguist', '~> 4.7.0', require: 'linguist'
 gem 'gitaly-proto', '~> 0.61.0', require: 'gitaly'
 gem 'activesupport'
+gem 'rdoc', '~> 4.2'
 gem 'gollum-lib', '~> 4.2', require: false
 gem 'gollum-rugged_adapter', '~> 0.4.4', require: false
 
diff --git a/ruby/Gemfile.lock b/ruby/Gemfile.lock
index f5844182970561a322654245fa47b3ca5725f88e..249a55d80e01526033dd6550c2f96910dbc79f1e 100644
--- a/ruby/Gemfile.lock
+++ b/ruby/Gemfile.lock
@@ -87,6 +87,7 @@ GEM
     rainbow (2.2.2)
       rake
     rake (12.1.0)
+    rdoc (4.3.0)
     rouge (2.2.1)
     rubocop (0.50.0)
       parallel (~> 1.10)
@@ -124,6 +125,7 @@ DEPENDENCIES
   gitlab-styles (~> 2.0.0)
   gollum-lib (~> 4.2)
   gollum-rugged_adapter (~> 0.4.4)
+  rdoc (~> 4.2)
 
 BUNDLED WITH
    1.16.0