no there is only one class Invoice and only one project in the workspace. If I remove "extends Model", I instantly get the function highlighted. But when I put it back, the error disappears. I tried with really dumb names which would make you smile so I'll not write them here, none of them triggered the error. Technically I can write $this->whateverAndItWontTriggerError() in the class. Doesn't matter which class, it doesn't work in different projects on WordPress, OctoberCMS, clean Laravel ...