How to use the Mendix validator in a widget?

After setting a value of a attribute in a custom widget I got a javascript error saying that I should first check the value using the mendix/validator.

I added the mendix/validator to the widget (documented on https://apidocs.mendix.com/6/client/module-mendix_validator.html) as this:

define([
    "dojo/_base/declare",
    "mendix/validator",
    "mxui/widget/_WidgetBase",

    ...

], function (declare, validator, _WidgetBase, ...

But this gives me an error in the build-report.txt (it is however working when I run locally):

error(311) Missing dependency. module: BootstrapInputAddons/widget/BootstrapInputAddons; dependency: mendix/validator

What am I doing wrong?