Lazy-loading in OneToOne-bidirectional associations not working for inverse side

I am referring to the following situation:
http://www.doctrine-project.org/documentation/manual/2_0/en/association-mapping#one-to-one,-bidirectional

In this example: if I fetch an object of type "Customer" from my database, a second query is executed immediately that fetches the corresponding "Cart" even if I do not access the $cart property of "Customer". Annotating fetch="LAZY" to the $cart property does not make any difference. This is even worse in case of self-referencing objects, e.g. those having at most one parent object and at most one child object. Here, all associations are created by single database queries at once (e.g. fetching the child object, then the child of the child object and so forth).

By contrast, OneToMany associations are lazy-loaded from the inverse side (as expected).

Perhaps I should add, that I am using annotation mappings for my entities (no YAML, no XML).