Running sweeper I get an error

[lourenzo]

/usr/local/lib/node_modules/sweeper/lib/sweeper.js:36
Object.keys(packageJSON.dependencies).forEach(function (dependency) {
^
TypeError: Object.keys called on non-object
at Function.keys (native)
at /usr/local/lib/node_modules/sweeper/lib/sweeper.js:36:16
at fs.js:266:14
at /usr/local/lib/node_modules/sweeper/node_modules/readdirp/node_modules/graceful-fs/graceful-fs.js:103:5
at Object.oncomplete (fs.js:107:15)

Running on Mac OS X 10.9.1, node 0.10.24