npm-run does not respect source-subdir

Given a part:

  my-part:
    # See 'snapcraft plugins'
    plugin: nodejs
    npm-run: [foo]
    source: .
    source-subdir: nodeapp

And a tree:
.
├── nodeapp
│   └── package.json
└── snap
    └── snapcraft.yaml

npm tries to find package.json in the root:

npm run foo
npm ERR! Linux 4.10.0-21-generic
npm ERR! argv "/tmp/nodejs-snap/parts/my-part/install/bin/node" "/tmp/nodejs-snap/parts/my-part/install/bin/npm" "run" "foo"
npm ERR! node v6.10.2
npm ERR! npm v3.10.10
npm ERR! path /tmp/nodejs-snap/parts/my-part/src/package.json
npm ERR! code ENOENT
npm ERR! errno -2
npm ERR! syscall open

npm ERR! enoent ENOENT: no such file or directory, open '/tmp/nodejs-snap/parts/my-part/src/package.json'
npm ERR! enoent ENOENT: no such file or directory, open '/tmp/nodejs-snap/parts/my-part/src/package.json'
npm ERR! enoent This is most likely not a problem with npm itself
npm ERR! enoent and is related to npm not being able to find a file.
npm ERR! enoent

npm ERR! Please include the following file with any support request:
npm ERR! /tmp/nodejs-snap/parts/my-part/src/npm-debug.log
Command '['/bin/sh', '/tmp/tmpri054knq', 'npm', 'run', 'foo']' returned non-zero exit status 254.