diff --git a/rack-rdf.gemspec b/rack-rdf.gemspec
index ab52efa..2fb9a08 100755
--- a/rack-rdf.gemspec
+++ b/rack-rdf.gemspec
@@ -28,7 +28,7 @@ Gem::Specification.new do |gem|
   gem.required_ruby_version      = '>= 3.0'
   gem.requirements               = []
   gem.add_runtime_dependency     'rdf',        '~> 3.3'
-  gem.add_runtime_dependency     'rack',       '>= 2.2', '< 4'
+  gem.add_runtime_dependency     'rack',       '~> 3.1'
 
   gem.add_development_dependency 'yard' ,      '~> 0.9'
   gem.add_development_dependency 'rspec',      '~> 3.12'
diff --git a/spec/rack_spec.rb b/spec/rack_spec.rb
index 52027ee..e95e75d 100644
--- a/spec/rack_spec.rb
+++ b/spec/rack_spec.rb
@@ -96,6 +96,7 @@ def app
           expect(options).to include(:link)
           link = options[:link]
           expect(link).to eq %(<foo>; rel="self")
+          ''
         end
         get '/', {}, {"HTTP_ACCEPT" => 'application/n-triples', "HTTP_LINK" => %(<foo>; rel="self")}
       end
@@ -115,6 +116,7 @@ def app
             expect(options).to include(:accept_params)
             accept_params = options[:accept_params]
             expect(accept_params).to include(profile: "http://www.w3.org/ns/json-ld#compacted http://example.org/white-listed")
+            ''
           end
           get '/', {}, {"HTTP_ACCEPT" => header}
         end