On my shining new Garmin Zumo XT I can't seem to be able to build unicode maps, when I start the device I get "Maps are corrupts and connot be used."

I'm using the latest and greatest mkgmap r4525, fresh pbf from geofabrik -  to reproduce:

wget http://download.geofabrik.de/europe/malta-latest.osm.pbf
java -jar ./mkgmap.jar --code-page=65001  \
 --family-id=10030 --product-id=1 --route --bounds=bounds.zip \
 --precomp-sea=sea.zip --gmapsupp   ./malta-latest.osm.pbf

Anything I can try? --code-page=1252 works as a charm

Thanks!
Enrico