diff --git a/css_splitter.gemspec b/css_splitter.gemspec
index b6b6a6e..2ca3f79 100644
--- a/css_splitter.gemspec
+++ b/css_splitter.gemspec
@@ -17,5 +17,5 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*"] + ["MIT-LICENSE", "Rakefile", "README.md"]
   s.test_files = Dir["test/**/*"]
 
-  s.add_dependency "rails", ">= 3.1"
+  s.add_dependency "rails", ">= 4.0.0"
 end