diff --git a/lib/omniauth/strategies/azure_oauth2.rb b/lib/omniauth/strategies/azure_oauth2.rb
index 20eee6a..947e486 100644
--- a/lib/omniauth/strategies/azure_oauth2.rb
+++ b/lib/omniauth/strategies/azure_oauth2.rb
@@ -25,7 +25,7 @@ def client
 
         options.client_id = provider.client_id
         options.client_secret = provider.client_secret
-        options.tenant_id = 
+        options.tenant_id =
           provider.respond_to?(:tenant_id) ? provider.tenant_id : 'common'
 
         options.authorize_params.domain_hint = provider.domain_hint if provider.respond_to?(:domain_hint) && provider.domain_hint
@@ -53,6 +53,9 @@ def client
         }
       end
 
+      def callback_url
+        full_host + script_name + callback_path
+      end
 
       def raw_info
         # it's all here in JWT http://msdn.microsoft.com/en-us/library/azure/dn195587.aspx
diff --git a/omniauth-azure-oauth2.gemspec b/omniauth-azure-oauth2.gemspec
index 128db48..0b3bdb0 100644
--- a/omniauth-azure-oauth2.gemspec
+++ b/omniauth-azure-oauth2.gemspec
@@ -19,7 +19,7 @@ Gem::Specification.new do |gem|
   gem.add_dependency 'omniauth', '~> 1.0'
   gem.add_dependency 'jwt', '~> 1.0'
 
-  gem.add_runtime_dependency 'omniauth-oauth2', '~> 1.1'
+  gem.add_runtime_dependency 'omniauth-oauth2', '~> 1.4'
 
   gem.add_development_dependency 'rspec', '>= 2.14.0'
   gem.add_development_dependency 'rake'