cbimport key generation unable to access nested field

The following cbimport statement fails:

cbimport json -f lines -d file://couchmusic1-countries.json -u Administrator -p password -b couchmusic1 -c localhost -g country::%country.countryCode%

The reported error is: Key generation for document failed, field with country.countryCode does not exist in document.

The field country.countryCode does exist for each document in the file (attached).