diff --git a/Gemfile.lock b/Gemfile.lock
index 60ba91b..89f72f5 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     compeon-rack_tools (0.3.0)
-      rack (~> 2.0)
+      rack (>= 2, < 4)
       rack-cors
 
 GEM
@@ -23,7 +23,7 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     psych (3.1.0)
-    rack (2.2.3.1)
+    rack (2.2.6.4)
     rack-cors (1.1.1)
       rack (>= 2.0.0)
     rack-test (1.1.0)
diff --git a/compeon-rack_tools.gemspec b/compeon-rack_tools.gemspec
index 541feda..da3563e 100644
--- a/compeon-rack_tools.gemspec
+++ b/compeon-rack_tools.gemspec
@@ -24,7 +24,7 @@ Gem::Specification.new do |spec|
   end
   spec.require_paths = ['lib']
 
-  spec.add_dependency 'rack', '~> 2.0'
+  spec.add_dependency 'rack', '>= 2', '< 4'
   spec.add_dependency 'rack-cors'
 
   spec.add_development_dependency 'bundler', '~> 2.0'