MVC5, Web API 2 and Ninject

I have created a new MVC5 project with Web API 2, I then added the Ninject.MVC3 package from NuGet.

Constructor injection is working fine for the MVC5 controllers, but i am getting an error when trying to use it with the Web API Controllers.

An error occurred when trying to create a controller of type 'UserProfileController'. Make sure that the controller has a parameterless public constructor.

Constructor for working MVC5 controller:

public class HomeController : Controller
{
    private IMailService _mail;
    private IRepository _repo;

    public HomeController(IMailService mail, IRepository repo)
    {
        _mail = mail;
        _repo = repo;
    }
}

Constructor for non-working Web API Controller:

public class UserProfileController : ApiController
{
    private IRepository _repo;

    public UserProfileController(IRepository repo)
    {
        _repo = repo;
    }
}

Below is the full NinjectWebCommon.cs file:

[assembly: WebActivator.PreApplicationStartMethod(typeof(DatingSite.App_Start.NinjectWebCommon), "Start")]
[assembly: WebActivator.ApplicationShutdownMethodAttribute(typeof(DatingSite.App_Start.NinjectWebCommon), "Stop")]

namespace DatingSite.App_Start
{
using System;
using System.Web;

using Microsoft.Web.Infrastructure.DynamicModuleHelper;

using Ninject;
using Ninject.Web.Common;
using DatingSite.Services;
using DatingSite.Data;

public static class NinjectWebCommon
{
    private static readonly Bootstrapper bootstrapper = new Bootstrapper();

    /// <summary>
    /// Starts the application
    /// </summary>
    public static void Start()
    {
        DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule));
        DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule));
        bootstrapper.Initialize(CreateKernel);
    }

    /// <summary>
    /// Stops the application.
    /// </summary>
    public static void Stop()
    {
        bootstrapper.ShutDown();
    }

    /// <summary>
    /// Creates the kernel that will manage your application.
    /// </summary>
    /// <returns>The created kernel.</returns>
    private static IKernel CreateKernel()
    {
        var kernel = new StandardKernel();
        kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
        kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();

        RegisterServices(kernel);
        return kernel;
    }

    /// <summary>
    /// Load your modules or register your services here!
    /// </summary>
    /// <param name="kernel">The kernel.</param>
    private static void RegisterServices(IKernel kernel)
    {
#if DEBUG
        kernel.Bind<IMailService>().To<MockMailService>().InRequestScope();

#else
        kernel.Bind<IMailService>().To<MailService>().InRequestScope();
#endif
        kernel.Bind<SiteContext>().To<SiteContext>().InRequestScope();
        kernel.Bind<IRepository>().To<Repository>().InRequestScope();
    }
}
}