Eager loading: what am I doing wrong?

I am trying to get eager loading to work.
So far it does have an effect on the initial query issued - though
not the desired on: it just mentions all the fields explicitly, but
creates no joins:

[4;36;1mCourse Load Including Associations (0.002771) [0m
[0;1mSELECT courses.id AS t0_r0, courses.name AS t0_r1,
courses.reference AS t0_r2, courses.subject_id AS t0_r3,
courses.course_type_id AS t0_r4, courses.description AS t0_r5,
courses.credits AS t0_r6, courses.lock_version AS t0_r7,
courses.created_on AS t0_r8, courses.updated_on AS t0_r9 FROM
courses ORDER BY name [0m

And then, when rendering, it churns out the myriad of individual
queries just as before.

Can anybody help me out with this?