Unresolved Symbol in Static Context and DataTrigger.Binding

I've got some DataTriggers where I get "Unresolved Symbol in Static Context" warnings.  I can't find a way to let the DataTrigger know the type of data context it's dealing with.

Example:

<DataTrigger Binding="{Binding Path=IsDropTarget}" Value="True">

The style is applied to an EditGridCellData object (from DevExpress data grid).  However, the DataContext is my own MainTreeNodeWrapper class.  If I add a DesignInstance to the DataTrigger it stops the warning but then won't compile because DesignInstance can't be applied to DataTrigger.

<DataTrigger Binding="{Binding Path=IsDropTarget}" Value="True" d:DataContext="{d:DesignInstance local:MainTreeNodeWrapper}">

Any ideas how to stop the warning?  Thanks.