Error Warning: Parameter 2 to ES_WP_Query_Shoehorn

[kclarke10]

Have got WP 4.8, on PHP 7.1.6 with searchpress.
On the site's static frontpage, I've set es => true on all the WP_Query there.
On categories, date and authors ..I set es via pre_get_posts

Everything looks to be working as expected but this error warning appears for every query:
Parameter 2 to ES_WP_Query_Shoehorn::filter__posts_request() expected to be a reference, value given

[dhanendrannewscorp]

I'm also getting the same error on the Query Monitor. Is there any fix for this issue?