diff --git a/grack.gemspec b/grack.gemspec
index 039fe94..f7f7491 100644
--- a/grack.gemspec
+++ b/grack.gemspec
@@ -15,6 +15,6 @@ Gem::Specification.new do |gem|
   gem.require_paths = ["lib"]
   gem.version       = Grack::VERSION
 
-  gem.add_dependency("rack", "~> 1.5.1")
+  gem.add_dependency("rack", ">= 1.5.1")
   gem.add_development_dependency("mocha", "~> 0.11")
 end