diff --git a/lib/ougai/version.rb b/lib/ougai/version.rb
index 777c4d2..ea0ab65 100644
--- a/lib/ougai/version.rb
+++ b/lib/ougai/version.rb
@@ -1,3 +1,3 @@
 module Ougai
-  VERSION = '1.6.0'
+  VERSION = '1.6.1'
 end
diff --git a/ougai.gemspec b/ougai.gemspec
index 9ccf1f0..ca89165 100644
--- a/ougai.gemspec
+++ b/ougai.gemspec
@@ -22,7 +22,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.required_ruby_version = '>= 2.1.2'
-  spec.add_development_dependency "oj", "~> 3.4"
+  spec.add_dependency "oj", "~> 3.4"
   spec.add_development_dependency "bundler", "~> 1.11"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rspec", "~> 3.0"