DropDownButton/SplitButton mouse over still works despite CanExecute of a Command returns false

[makingbloke]

Hi,

I have the following XAML:

<DropDownButton Width="55" Height="45" ToolTip="Save Attachments" Command="{Binding AttachmentsCommand}" ItemsSource="{Binding AttachmentsMenu}" />

AttachmentsCommand is a RelayCommand (I'm using MVVM Light). If the CanExecuteAttachmentsCommand function returns false then the button part of the DropDownButton is disabled, but the DropDown arrow still changes colour when the mouse moves over it (even though it appears disabled). If the DropDown arrow is disabled by the command then it should ignore mouseover (if I set IsEnabled to false this works correctly).

I'm using version the latest 1.6.4 from Nuget.

Thanks