diff --git a/.travis.yml b/.travis.yml
index c5edd15c..da409b6b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,8 @@ language: ruby
 rvm:
   - 1.8.7
   - 1.9.2
-
+  - 2.2.5
+  - 2.4.2
 notifications:
   email:
     recipients:
diff --git a/bio-nexml.gemspec b/bio-nexml.gemspec
index efa0d19c..cd903e37 100644
--- a/bio-nexml.gemspec
+++ b/bio-nexml.gemspec
@@ -20,6 +20,7 @@ Gem::Specification.new do |s|
   s.add_dependency('libxml-ruby', '= 3.0.0')
 
   s.add_development_dependency('test-unit', '~> 3.2.3')
+  s.add_development_dependency('rdoc')
 
   # gem
   s.files         = `git ls-files`.split("\n") rescue ''