MouseEnter event in custom control not firing first time

I have made a custom control and added a MouseEnter event to the LayoutRoot.

I added the custom control to my main usercontrol. It is inside a grid, which is inside a PanelDragDropTarget, which is in another grid.

The problem I have, is that the MouseEnter event is not fired the first time the mouse enters the custom control. After the first time it works normally.

How can I make sure the MouseEnter event is fired the first time the mouse enters the custom control?