diff --git a/lib/mailup.rb b/lib/mailup.rb
index bcc57ec..966d510 100644
--- a/lib/mailup.rb
+++ b/lib/mailup.rb
@@ -168,6 +168,13 @@ def handle_response(response) # :nodoc:
         raise BadRequest.new response.parsed
       when 401
         raise Unauthorized.new
+      when 403
+        case response.body
+        when /Too many requests/i
+          raise TooManyRequests.new
+        else
+          raise ClientError.new response.parsed
+        end
       when 404
         raise NotFound.new
       when 400...500
@@ -226,4 +233,4 @@ def stats
     end
 
   end
-end
\ No newline at end of file
+end
diff --git a/mailup.gemspec b/mailup.gemspec
index 3166ad6..6fdf026 100644
--- a/mailup.gemspec
+++ b/mailup.gemspec
@@ -19,7 +19,7 @@ Gem::Specification.new do |gem|
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
   gem.require_paths = ["lib"]
 
-  gem.add_runtime_dependency 'oauth2', '~> 0.9', '>= 0.9.2'
+  gem.add_runtime_dependency 'oauth2', '~> 1.0'
 
   gem.add_development_dependency "rspec"
   gem.add_development_dependency "rake"