Inconsistent accessibility property type is less accessible than

I'm getting an error "Inconsistent accessibility property type 'List<MasterPageItem' is less accessible than property MainPage.MenuList

This is my code

using ACPlus_MobileEPOS.MenuItems;
using ACPlus_MobileEPOS.Views;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace ACPlus_MobileEPOS {
    public partial class MainPage : MasterDetailPage
    {
        public List<MasterPageItem> MenuList
        {
            get;
            set;
        }

        public MainPage()
        {
            InitializeComponent();

            MenuList = new List<MasterPageItem>();

            MenuList.Add(new MasterPageItem()
            {
                Title = "EPOS",
                TargetType = typeof(pgEPOS)
            });

            MenuList.Add(new MasterPageItem()
            {
                Title = "System",
                TargetType = typeof(pgSystem)
            });

            MenuList.Add(new MasterPageItem()
            {
                Title = "Receipts",
                TargetType = typeof(pgReceipts)
            });

            MenuList.Add(new MasterPageItem()
            {
                Title = "End of Day",
                TargetType = typeof(pgEOD)
            });

            MenuList.Add(new MasterPageItem()
            {
                Title = "Reports",
                TargetType = typeof(pgReports)
            });

            MenuList.Add(new MasterPageItem()
            {
                Title = "Session",
                TargetType = typeof(pgSession)
            });

            navigationDrawerList.ItemsSource = MenuList;
            Detail = new NavigationPage((Page)Activator.CreateInstance(typeof(pgEPOS)));
        }

        private void OnMenuItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            var item = (MasterPageItem)e.SelectedItem;
            Type page = item.TargetType;
            Detail = new NavigationPage((Page)Activator.CreateInstance(page));
            IsPresented = false;
        }
    }
}

I think it's something to do with the class being declared as public partial, but I'm not totally sure,

How do I fix this?