diff --git a/tasks/gem.rake b/tasks/gem.rake
index 0919afc6..24d9714b 100644
--- a/tasks/gem.rake
+++ b/tasks/gem.rake
@@ -21,7 +21,7 @@ namespace :gem do
 
     s.required_ruby_version = ">= 2.2"
 
-    s.add_runtime_dependency "public_suffix", ">= 2.0.2", "< 5.0"
+    s.add_runtime_dependency "public_suffix", ">= 2.0.2", "< 6.0"
     s.add_development_dependency "bundler", ">= 1.0", "< 3.0"
 
     s.require_path = "lib"