Why am i getting this ember-font-awesome error?

I upgraded the current Ember app from 3.20 to 3.26 and we are getting this error from ember-font-awesome.

Template Compiler Error (broccoli-persistent-filter:TemplateCompiler) in ember-font-awesome/components/fa-icon/template.hbs

loc$$1.sliceStartChars is not a function

Any quick ideas before I jump down a rabbit hole?