diff --git a/oauth2.gemspec b/oauth2.gemspec
index 11eb83c1..d1a6e1c5 100644
--- a/oauth2.gemspec
+++ b/oauth2.gemspec
@@ -8,7 +8,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'faraday', ['>= 0.8', '< 0.10']
   spec.add_dependency 'multi_json', '~> 1.3'
   spec.add_dependency 'multi_xml', '~> 0.5'
-  spec.add_dependency 'rack', '~> 1.2'
+  spec.add_dependency 'rack', '>= 1.2', '< 4.0'
   spec.add_dependency 'jwt', '~> 0.1.8'
   spec.authors       = ['Michael Bleigh', 'Erik Michaels-Ober']
   spec.cert_chain    = %w(certs/sferik.pem)