diff --git a/Gemfile b/Gemfile
index b3ef82291e..1efe52cc58 100644
--- a/Gemfile
+++ b/Gemfile
@@ -44,5 +44,5 @@ end
 # `bundle config set --local without rdoc`
 # Then re-run `bundle install`.
 group :rdoc do
-  gem "rdoc", "6.6.2"
+  gem "rdoc", "6.6.3.1"
 end