[ionic 4] ion-back-button

Hi, I’m trying to add a back button with the menu-button, but isn’t showing, just the menu button. Anyone can help me?

<ion-header>
	<ion-toolbar >
		<ion-buttons  slot="start">
      <ion-menu-button></ion-menu-button>
      <ion-back-button slot="end"></ion-back-button>    
    </ion-buttons>
		<ion-title class="titleToolbar">
			LISTAS SALVAS
		</ion-title>
	</ion-toolbar>
</ion-header>