diff --git a/cms_scanner.gemspec b/cms_scanner.gemspec
index 0e9e3ea..d45b8b5 100644
--- a/cms_scanner.gemspec
+++ b/cms_scanner.gemspec
@@ -23,7 +23,7 @@ Gem::Specification.new do |s|
   s.add_dependency 'get_process_mem', '~> 0.2.5'
   s.add_dependency 'nokogiri', '~> 1.16'
   s.add_dependency 'opt_parse_validator', '~> 1.9.5'
-  s.add_dependency 'public_suffix', '>= 4.0.3', '< 5.1.0'
+  s.add_dependency 'public_suffix', '>= 4.0.3', '< 6.1'
   s.add_dependency 'ruby-progressbar', '>= 1.10', '< 1.14'
   s.add_dependency 'typhoeus', '>= 1.3', '< 1.5'
   s.add_dependency 'xmlrpc', '~> 0.3'