The goal is to emit XML with namespaces aggregated at the document root, and with prefixes customised. data.xml provides aggregate-xmlns for this. Unfortunately it seems to interfere with xmlns prefix :attrs.

To reproduce first set up some test data:

Namespace aggregation with (xml/aggregate-xmlns document) works fine, but now I would like to customise the prefixes. Here the :attrs seem to have no effect:

Doing aggregate-xmlns last instead throws an exception:

I could verify that the right prefixes are generated when I leave aggregate-xmlns out of the picture - but aggregation is the goal.