diff --git a/Gemfile b/Gemfile
index 4f2d019..ecc2f33 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,6 +9,6 @@ group :development, :test do
   gem "bundler", ">= 1.16", "< 3.0"
   gem "rake-compiler", "~> 1.0"
   gem "rake-compiler-dock", "~> 1.0"
-  gem "rdoc", "~> 5.1"
+  gem "rdoc", "~> 6.4"
   gem "rspec", "~> 3.5"
 end