Ion-badge inside ion-tab-button

I am trying to add a badge to a tab button:

    <ion-tab-button tab="inbox">
      <ion-badge slot="start">10</ion-badge>      
      <ion-icon aria-hidden="true" name="mail"></ion-icon>

but the badge just never shows up. If try the badge on the content, with an item list or a button, then it shows up correctly, so the problem seems to be related to the ion-tabs. Any one has solved this ?


Answering myself: just remove the slot property.