UISplitViewController - prevent splitting in landscape on iPhone 6 plus

I am using a UISplitViewController in my app. This works just fine on iPad where primary and secondary are always visible, and it works just fine on most iPhones where it acts like a UINavigationController.

On iPhone 6+ and 6S+ the split view acts like an iPhone in portrait and like an iPad in landscape. This splitting in landscape is causing me problems and I'd like to avoid it.

Is there any way to prevent the UISplitViewController from showing primary and secondary controllers in iPhone 6+ landscape? I just want it to show the secondary controller, the same as it would do for other iPhones.

Thanks.

I was able to do this by subclassing the UISplitViewController and then overriding the trait collection to return a compact horizontal size class when the device is not an iPad. I know checking the interface idiom is a faux-pas these days, but I wasn't sure how else to do it.

I simply added this method to my UISplitViewController subclass:

-(UITraitCollection *)traitCollection {
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        return [super traitCollection];
    } else {
        return [UITraitCollection traitCollectionWithHorizontalSizeClass:UIUserInterfaceSizeClassCompact];
    }
}

Any suggestions for a better way to do this are certainly welcome.