ViewModel does not exsist in namespace, But it does

Got this Code:
 d:DataContext="{d:DesignInstance Type=main:CloseReasonViewModel,
    IsDesignTimeCreatable=False}">

Xaml gives me autocomplete on CloseReasonViewModel
However Im getting a warning on that line that the ViewModel doesn't exist, which is does with the correct namespace.
I've got more viewModels there and Views and they work fine, with the same namespace.
What could be the problem?
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