https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18643

--- a/Gemfile
+++ b/Gemfile
@@ -146,7 +146,7 @@
 gem 'creole', '~> 0.5.0'
 gem 'wikicloth', '0.8.1'
 gem 'asciidoctor', '~> 1.5', '>= 1.5.6'
-gem 'asciidoctor-plantuml', '0.0.8'
+gem 'asciidoctor-plantuml', '~> 0.0.8'
 gem 'rouge', '~> 2.0'
 gem 'truncato', '~> 0.7.9'
 gem 'bootstrap_form', '~> 2.7'