Django Haystack Xapian: Default AND Chaining, among others, not working

Here is my haystack config:

HAYSTACK_CONNECTIONS = {
    'default': {
        'ENGINE': 'xapian_backend.XapianEngine',
        'PATH': os.path.join(BASE_DIR, 'xapian_index'),
        'INCLUDE_SPELLING': True,
        'BATCH_SIZE': 100,
    },
}

I'm using haystack's views.SearchView

All packages including Xapian updated to their latest version yesterday.

I'm searching a vegetables and locations index. When I search for 'carrot California' (without quotes), I get results from all over the place, and different vegetables too. When I search for 'carrot and California', or 'carrot+California', the same thing happens. However, when I search for 'carrot AND California', I get the right results.

I manually set HAYSTACK_DEFAULT_OPERATOR = 'AND', but that didn't work either.

Is there a setting I'm missing?

The larger question though is, what is the best/optimal configuration for Haystack+Xapian?

This was an error of Xapian-Haystack that was meanwhile solved.