Why isn't the lock screen clock background darkened on my iPhone 6 plus?

Hi,

yesterday i swapped from an iPhone 6 to an iPhone 6 plus. I want to use the same wallpaper on the 6 plus, which i previously used on my 6. But there is a problem. When i choose the picture on my iPhone 6 and tap "set as wallpaper", it shows me the preview with the clock background darkened, so that i can see the time and the Informations on top of my screen (e.g. Carrier, battery, etc.). When i try exactly the same on my iPhone 6 plus, the clock background is not darkened, so that i can't see the time and the informations on the top of the screen as you can see on the screenshots below. Does anyone have the same issue?