diff --git a/shibboleth-rails.gemspec b/shibboleth-rails.gemspec
index 8e624e3..0be42a8 100644
--- a/shibboleth-rails.gemspec
+++ b/shibboleth-rails.gemspec
@@ -18,5 +18,5 @@ Gem::Specification.new do |s|
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ["lib"]
 
-  s.add_runtime_dependency "rails", '~> 3.0'
+  s.add_runtime_dependency "rails", '>= 3', '< 7'
 end