diff --git a/redis-session-store.gemspec b/redis-session-store.gemspec
index 0544efc..af35027 100644
--- a/redis-session-store.gemspec
+++ b/redis-session-store.gemspec
@@ -17,7 +17,7 @@ Gem::Specification.new do |gem|
                     .match(/^  VERSION = '(.*)'/)[1]
 
   gem.add_runtime_dependency 'redis', '~> 3'
-  gem.add_runtime_dependency 'actionpack', '>= 3', '< 5.1'
+  gem.add_runtime_dependency 'actionpack', '>= 3'
 
   gem.add_development_dependency 'fakeredis', '~> 0.5'
   gem.add_development_dependency 'rake', '~> 11'