diff --git a/capybara-webkit.gemspec b/capybara-webkit.gemspec
index 1f2ab6c..3874056 100644
--- a/capybara-webkit.gemspec
+++ b/capybara-webkit.gemspec
@@ -16,6 +16,8 @@ Gem::Specification.new do |s|
 
   s.extensions = "extconf.rb"
 
+  s.required_ruby_version = ">= 1.9.0"
+
   s.add_runtime_dependency("capybara", "~> 2.0", ">= 2.0.2")
   s.add_runtime_dependency("json")