diff --git a/lib/rack/request.rb b/lib/rack/request.rb
index 248ce18..eae04ed 100644
--- a/lib/rack/request.rb
+++ b/lib/rack/request.rb
@@ -63,9 +63,17 @@ module Rack
       media_type_params['charset']
     end
 
+    def raw_host_with_port
+      if forwarded = @env["HTTP_X_FORWARDED_HOST"]
+        forwarded.split(/,\s?/).last
+      else
+        @env['HTTP_HOST'] || "#{@env['SERVER_NAME'] || @env['SERVER_ADDR']}:#{@env['SERVER_PORT']}"
+      end
+    end
+
     def host
       # Remove port number.
-      (@env["HTTP_HOST"] || @env["SERVER_NAME"]).to_s.gsub(/:\d+\z/, '')
+      raw_host_with_port.to_s.gsub(/:\d+\z/, '')
     end
 
     def script_name=(s); @env["SCRIPT_NAME"] = s.to_s             end
diff --git a/test/spec_rack_request.rb b/test/spec_rack_request.rb
index fe000c2..da1b78b 100644
--- a/test/spec_rack_request.rb
+++ b/test/spec_rack_request.rb
@@ -35,8 +35,17 @@ context "Rack::Request" do
     req.host.should.equal "www2.example.org"
 
     req = Rack::Request.new \
-      Rack::MockRequest.env_for("/", "SERVER_NAME" => "example.org:9292")
+      Rack::MockRequest.env_for("/", "SERVER_NAME" => "example.org", "SERVER_PORT" => "9292")
     req.host.should.equal "example.org"
+    
+    req = Rack::Request.new \
+      Rack::MockRequest.env_for("/", "HTTP_HOST" => "localhost:81", "HTTP_X_FORWARDED_HOST" => "example.org:9292")
+    req.host.should.equal "example.org"
+
+    env = Rack::MockRequest.env_for("/", "SERVER_ADDR" => "192.168.1.1", "SERVER_PORT" => "9292")
+    env.delete("SERVER_NAME")
+    req = Rack::Request.new(env)
+    req.host.should.equal "192.168.1.1"
 
     env = Rack::MockRequest.env_for("/")
     env.delete("SERVER_NAME")