Ionic 4 ion-menu is only working on left-hand side, will not appear on right-hand side

Hi All,
I have an app running Ionic 4, and I’m having issues getting the ion-menu to show on the right side of the page. No matter what I spec in the side attibute, it shows on the left or start. Any ideas?

<ion-split-pane when="md">
    <ion-nav [root]="rootPage" main #content ></ion-nav>
    <ion-menu side="end">
        <ion-nav  [root]="activitiesPage" ></ion-nav>


ionic (Ionic CLI) : 4.0.3 (/Users/zsoflin/.npm-global/lib/node_modules/ionic)
Ionic Framework : @ionic/angular 4.0.0-beta.0
@angular-devkit/core : 0.7.0-rc.3
@angular-devkit/schematics : 0.7.0-rc.3
@angular/cli : 6.0.8
@ionic/ng-toolkit : 1.0.0
@ionic/schematics-angular : 1.0.1


NodeJS : v8.11.3 (/usr/local/bin/node)
npm : 5.6.0
OS : macOS High Sierra