organize and stage keywords together mess up file conflict checking

The following snapcraft.yaml section gives a file conflict error ("Parts 'part1' and 'part2' have the following file paths in common which have different contents"):

parts:
  part1:
    plugin: dump
    source: ./src1
    organize:
      '*': opt/
    stage:
      - -opt/commonfile.txt
  part2:
    plugin: dump
    source: ./src2
    organize:
      '*': opt/
    stage:
      - -opt/commonfile.txt

However, when both stage keywords are changed to

    stage:
      - -commonfile.txt

no errors are given, but commonfile.txt is copied into stage (with the later one overwriting the first).

See attachment for full example.