diff --git a/braintreejs-rails.gemspec b/braintreejs-rails.gemspec
index f2d598d..ba41fba 100755
--- a/braintreejs-rails.gemspec
+++ b/braintreejs-rails.gemspec
@@ -16,5 +16,5 @@ Gem::Specification.new do |gem|
   gem.executables   = gem.files.grep(%r{^bin/}).map{ |f| File.basename(f) }
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
   gem.require_paths = ["lib"]
-  gem.add_dependency "railties", "~> 3.1"
+  gem.add_dependency "railties", "~> 4.0"
 end