Bookmarks corrupted under pdf/ua-2

As I need to produce tagged PDF I am using \setupbackend[format={pdf/ua-2}]
The tagged PDF is great. 

Only the bookmarks are corrupted when non-ASCII is used:


\setupinteraction[state=start]

\setupbackend[format={pdf/ua-2}]
%\setupbackend[format={pdf/ua-1}]

\placebookmarks[chapter][]

\starttext

\chapter{Äpfel – Öl}

\stoptext




Steffen
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