diff --git a/Gemfile b/Gemfile
index ac640f8..f572ea0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,6 +6,6 @@ gem "asciidoctor", "2.0.16"
 gem "commonmarker", "=0.21.0"
 gem "creole", "=0.5.0"
 gem "org-ruby", "=0.9.12"
-gem "rdoc", "6.3.2"
+gem "rdoc", "6.4.0"
 gem "redcarpet", "3.5.1"
 gem "wikicloth", "=0.8.3"