WPF Generic.xaml with Visual Studio 2015

I just wanted to migrate our Project to the new Visual Studio 2015. Unfortunately I got a problem with the Generic.xaml. I have a user control in a separate assembly and put all styling stuff in a seperate xaml file. This file I referenced in the Generic.xaml. It worked so fare. After the Migration a XML parse exception was thrown.

If I put the styling stuff directly into the Generic.xaml it works.

<Style TargetType="{x:Type outlookBarCtrl:MyButton}" BasedOn="{StaticResource {x:Type Button}}"><Setter Property="Foreground" Value="Green"/><Setter Property="Background" Value="Crimson"/></Style>

If reference a file, a exception occurs.

<ResourceDictionary.MergedDictionaries><ResourceDictionary Source="OutlookBarCtrl;component/Styles/MyButtonStyles.xaml"/></ResourceDictionary.MergedDictionaries>

Does anyone have an idea why this happens? 

Thanks for answers.

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