build fails in docker but not elsewhere.

[okolloen]

• polymer build
  info: [cli.command.build] Clearing build/ directory...
  info: [cli.build.build] (es6-unbundled) Building...
  error: [cli.main] Uncaught exception: RangeError [ERR_OUT_OF_RANGE]: The value of "mode" is out of range. Received 33206
  error: [cli.main] RangeError [ERR_OUT_OF_RANGE]: The value of "mode" is out of range. Received 33206
  at Object.fs.fchmod (fs.js:1056:11)
  at Object.fchmod (/usr/local/lib/node_modules/polymer-cli/node_modules/graceful-fs/polyfills.js:237:17)
  at mode (/usr/local/lib/node_modules/polymer-cli/node_modules/vinyl-fs/lib/fileOperations.js:132:10)
  at onStat (/usr/local/lib/node_modules/polymer-cli/node_modules/vinyl-fs/lib/fileOperations.js:125:14)
  at /usr/local/lib/node_modules/polymer-cli/node_modules/graceful-fs/polyfills.js:287:18
  at FSReqWrap.oncomplete (fs.js:183:5)

A clue might be : isaacs/node-graceful-fs#129