diff --git a/Gemfile b/Gemfile
index 1567366..f97c3f7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'awesome_print', '1.9.2'
 
 gem 'asciidoctor-fb2', '0.8.0'
 gem 'asciidoctor-epub3', '2.3.0'
-gem 'asciidoctor-pdf', '2.3.19'
+gem 'asciidoctor-pdf', '2.3.20'
 
 gem 'coderay', '1.1.3'
 gem 'pygments.rb', '4.0.0'