diff --git a/rest-client.gemspec b/rest-client.gemspec
index 967457c2..9f96ece5 100644
--- a/rest-client.gemspec
+++ b/rest-client.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency('rspec', '~> 2.4')
   s.add_development_dependency('pry')
   s.add_development_dependency('pry-doc')
-  s.add_development_dependency('rdoc', '>= 2.4.2', '< 5.0')
+  s.add_development_dependency('rdoc', '>= 2.4.2', '<= 6.6.2')
 
   s.add_dependency('http-cookie', '>= 1.0.2', '< 2.0')
   s.add_dependency('mime-types', '>= 1.16', '< 3.0')