Spoonsful / Spoonfuls

A quick browse has Merriam Webster, and Cambridge org both giving both plurals.
Collins & Oxford both give 'spoonfuls' with no alternative.

My own preference would be spoonfuls. 'Spoonsful' always sounds to me as if more than one spoon is being used.

Strangely whatever spellchecker my computer is using picks up 'spoonfuls' as being the wrong spelling, although it is given in all four dictionaries that I checked.