Path Expected for Join! Nhibernate Error

I trying to do a join and I keep getting this error

Path expected for join! [SELECT t.CourseId FROM Task as t INNER JOIN Courses as c, CoursePermissions as cp WHERE (t.CourseId = 1)]

I have

const string query = "SELECT t.CourseId FROM  Task as t INNER JOIN Courses as c, CoursePermissions as cp WHERE (t.CourseId = 1)";

var a = session.CreateQuery(query);

My Sql I am trying to achieve

SELECT     dbo.Tasks.CourseId
FROM         dbo.Tasks INNER JOIN
                      dbo.Courses ON dbo.Tasks.CourseId = dbo.Courses.CourseId INNER JOIN
                      dbo.CoursePermissions ON dbo.Courses.CourseId = dbo.CoursePermissions.CourseId
WHERE     (dbo.Tasks.CourseId = 1)

I am using nhibernate 3.1 and fluent nhibernate 1.2