JavaScript error when blurring from field in a non-regular form

In Low Search’s lexicon, I’ve got a field I use for ajax lookups. When blurring out of the field, a JS error is triggered by some form validation script:

TypeError: true is not a function

most likely triggered by a function called _toggleErrorForFields, and specifically:

this._validationCallbacks[cleanField](message == 'success', message.error, field);

(according to the inspector)

Is there any way to not activate validation here?