diff --git a/lib/capybara/driver/webkit/browser.rb b/lib/capybara/driver/webkit/browser.rb
index 2edca38..56555ec 100644
--- a/lib/capybara/driver/webkit/browser.rb
+++ b/lib/capybara/driver/webkit/browser.rb
@@ -4,6 +4,8 @@ require 'json'
 
 class Capybara::Driver::Webkit
   class Browser
+    attr :server_port
+
     def initialize(options = {})
       @socket_class = options[:socket_class] || TCPSocket
       start_server
@@ -84,7 +86,7 @@ class Capybara::Driver::Webkit
 
     def discover_server_port(read_pipe)
       return unless IO.select([read_pipe], nil, nil, 10)
-      ((read_pipe.first || '').match(/listening on port: (\d+)/) || [])[1]
+      ((read_pipe.first || '').match(/listening on port: (\d+)/) || [])[1].to_i
     end
 
     def connect
diff --git a/spec/browser_spec.rb b/spec/browser_spec.rb
new file mode 100644
index 0000000..62a5093
--- /dev/null
+++ b/spec/browser_spec.rb
@@ -0,0 +1,27 @@
+require 'spec/spec_helper'
+require 'capybara/driver/webkit/browser'
+
+describe Capybara::Driver::Webkit::Browser do
+
+  let(:browser) { Capybara::Driver::Webkit::Browser.new }
+
+  describe '#server_port' do
+    subject { browser.server_port }
+    it 'returns a valid port number' do
+      should be_a(Integer)
+    end
+
+    it 'returns a port in the allowed range' do
+      should > 0x400
+      should < 0xffff
+    end
+  end
+
+  context 'random port' do
+    it 'chooses a new port number for a new browser instance' do
+      new_browser = Capybara::Driver::Webkit::Browser.new
+      new_browser.server_port.should_not == browser.server_port
+    end
+  end
+
+end