diff --git a/nokogiri-happymapper.gemspec b/nokogiri-happymapper.gemspec
index b4bc3d1..337c145 100644
--- a/nokogiri-happymapper.gemspec
+++ b/nokogiri-happymapper.gemspec
@@ -30,7 +30,7 @@ Gem::Specification.new do |spec|
 
   spec.extra_rdoc_files = ["README.md", "CHANGELOG.md", "License"]
 
-  spec.add_runtime_dependency "nokogiri", "~> 1.5"
+  spec.add_dependency "nokogiri", "~> 1.5"
 
   spec.add_development_dependency "pry", "~> 0.14.0"
   spec.add_development_dependency "rake", "~> 13.0"