Got an error while deriving changes

I'm trying to derive changes between 2 OSM files and export them in a new OSC file

osmosis --read-xml file="two.osm" --read-xml file="one.osm" --derive-change --write-xml-change file="AA.osc"

but I'm getting this error

SEVERE: Thread for task 1-read-xml failed
org.openstreetmap.osmosis.core.OsmosisRuntimeException: Only one bound element allowed.