diff --git a/Gemfile b/Gemfile
index 4ffb285..93cbb59 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,5 +9,5 @@ group :jekyll_plugins do
   gem 'jekyll-sitemap', '~> 1.0.0'
 end
 
-gem 'asciidoctor', '~> 1.5.4'
+gem 'asciidoctor', '~> 1.5.8'
 gem 'coderay', '1.1.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index cb30b83..62ae9c8 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -3,7 +3,7 @@ GEM
   specs:
     addressable (2.8.0)
       public_suffix (>= 2.0.2, < 5.0)
-    asciidoctor (1.5.5)
+    asciidoctor (1.5.8)
     coderay (1.1.1)
     colorator (1.1.0)
     concurrent-ruby (1.1.3)
@@ -92,7 +92,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  asciidoctor (~> 1.5.4)
+  asciidoctor (~> 1.5.8)
   coderay (= 1.1.1)
   jekyll
   jekyll-asciidoc