diff --git a/Gemfile.lock b/Gemfile.lock
index 8b34feb..d35f50b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,15 +2,15 @@ PATH
   remote: .
   specs:
     puma-websockets (0.1.0)
-      puma (~> 4.0)
+      puma (>= 4, < 6)
       websocket-driver (~> 0.7)
 
 GEM
   remote: https://rubygems.org/
   specs:
     diff-lcs (1.3)
-    nio4r (2.4.0)
-    puma (4.0.1)
+    nio4r (2.5.8)
+    puma (5.6.4)
       nio4r (~> 2.0)
     rake (10.5.0)
     rspec (3.8.0)
diff --git a/puma-websockets.gemspec b/puma-websockets.gemspec
index 8bd3e1f..6c369c0 100644
--- a/puma-websockets.gemspec
+++ b/puma-websockets.gemspec
@@ -27,6 +27,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rake', '~> 10.0'
   spec.add_development_dependency 'rspec', '~> 3.0'
 
-  spec.add_runtime_dependency 'puma', '~> 4.0'
+  spec.add_runtime_dependency 'puma', '>= 4', '< 6'
   spec.add_runtime_dependency 'websocket-driver', '~> 0.7'
 end