Problem with SQLite Example2

I'm looking at the "An Introduction to Xamarin.Forms and SQLite" example found at,

http://code.tutsplus.com/tutorials/an-introduction-to-xamarinforms-and-sqlite--cms-23020

in the RandomThoughtsPage.cs file, I receive the error;

Inconsistent accessibility: parameter type 'RandomThoughtDatabase' is less accessible than method 'RandomThoughtsPage.RandomThoughtsPage(RandomThoughtDatabase)'

this occurs in the following line;

public RandomThoughtsPage(RandomThoughtDatabase database)