Apply style to a specific element does not work with Safari

I am trying to apply the below CSS to a specific element on the HTML page, it works perfectly on Chrome; however, in Safari it does not.

CSS:

  #customNav > .toolbar-background {
  background: none;
  border:0;
  }

HTML:

<ion-navbar id="customNav" *navbar>
 <div class="toolbar-background"></div>
</ion-navbar>

Anyone knows how I can make it work for Safari too?