I have the following Storyboard: 'LayoutMargin' is a dependency property defined in the ancestor Window. This is the problem I'm having: The first time I run the animation it doesn't work - as if the LayoutMargin.Value isn't set. However, the second time I run the animation, and all subsequent times I run the animation, it work just fine. At first I suspected the LayoutMargin.Value was not set prior to the first animation, but it is set. Does anyone have any ideas about why this is happening?