diff --git a/.gitignore b/.gitignore
index 32ef4b9..a94a097 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@ log/*
 measurement/*
 pkg/*
 .DS_Store
+.tool-versions
diff --git a/Gemfile b/Gemfile
index 9f08f3a..4a3feea 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-gem 'jruby-openssl', '~> 0.10.5', :platforms => :jruby
+gem 'jruby-openssl', '~> 0.10.5', platforms: :jruby
 gem 'rake', '>= 12.0'
 gem 'yard', '>= 0.9.11'
 
@@ -13,17 +13,16 @@ end
 
 group :test do
   gem 'coveralls_reborn', '~> 0.19.0', require: false
-  gem 'hashie', '>= 3.4.6', '~> 4.0.0', :platforms => [:jruby_18]
-  gem 'json', '~> 2.3.0', :platforms => %i[jruby_18 jruby_19 ruby_19]
-  gem 'mime-types', '~> 3.1', :platforms => [:jruby_18]
-  gem 'rack', '>= 2.0.6', :platforms => %i[jruby_18 jruby_19 ruby_19 ruby_20 ruby_21]
+  gem 'hashie', '>= 3.4.6', '~> 4.0.0', platforms: [:jruby_18]
+  gem 'json', '~> 2.3.0', platforms: %i[jruby_18 jruby_19 ruby_19]
+  gem 'mime-types', '~> 3.1', platforms: [:jruby_18]
   gem 'rack-test'
-  gem 'rest-client', '~> 2.0.0', :platforms => [:jruby_18]
+  gem 'rest-client', '~> 2.0.0', platforms: [:jruby_18]
   gem 'rspec', '~> 3.5'
   gem 'rack-freeze'
-  gem 'rubocop', '>= 0.58.2', '< 0.69.0', :platforms => %i[ruby_20 ruby_21 ruby_22 ruby_23 ruby_24]
+  gem 'rubocop', '>= 0.58.2', '< 0.69.0', platforms: %i[ruby_20 ruby_21 ruby_22 ruby_23 ruby_24]
   gem 'simplecov-lcov'
-  gem 'tins', '~> 1.13', :platforms => %i[jruby_18 jruby_19 ruby_19]
+  gem 'tins', '~> 1.13', platforms: %i[jruby_18 jruby_19 ruby_19]
 end
 
 gemspec
diff --git a/lib/omniauth/builder.rb b/lib/omniauth/builder.rb
index 2882076..5843439 100644
--- a/lib/omniauth/builder.rb
+++ b/lib/omniauth/builder.rb
@@ -26,7 +26,7 @@ module OmniAuth
       @options = options
     end
 
-    def provider(klass, *args, &block)
+    def provider(klass, *args, **opts, &block)
       if klass.is_a?(Class)
         middleware = klass
       else
@@ -37,8 +37,7 @@ module OmniAuth
         end
       end
 
-      args.last.is_a?(Hash) ? args.push(options.merge(args.pop)) : args.push(options)
-      use middleware, *args, &block
+      use middleware, *args, **options.merge(opts), &block
     end
 
     def call(env)
diff --git a/omniauth.gemspec b/omniauth.gemspec
index dc0a90f..640d2be 100644
--- a/omniauth.gemspec
+++ b/omniauth.gemspec
@@ -6,7 +6,7 @@ require 'omniauth/version'
 
 Gem::Specification.new do |spec|
   spec.add_dependency 'hashie', ['>= 3.4.6']
-  spec.add_dependency 'rack', ['>= 1.6.2', '< 3']
+  spec.add_dependency 'rack', '~> 2.2.3'
   spec.add_development_dependency 'bundler', '~> 2.0'
   spec.add_dependency 'rack-protection'
   spec.add_development_dependency 'rake', '~> 12.0'