diff --git a/Gemfile b/Gemfile
index 60c316aa..3bb1e7df 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,5 +13,5 @@ gem 'coderay', '1.1.3'
 gem 'pygments.rb', '2.3.0'
 gem 'thread_safe', '0.3.6'
 gem 'epubcheck-ruby', '4.2.6.0'
-gem 'html-proofer', '4.4.1'
+gem 'html-proofer', '5.0.6'
 gem 'kindlegen', '3.1.1'