Error when providing path option in format { propName: glob.sync(...) }

[jeggett]

When I set paths parameter in the following format

paths: { app: glob.sync(`${PATHS.app}/*`)  },

But when I use following format: paths: glob.sync(${PATHS.app}/*) everything is working fine.

I got following error:

/home/jeggett/WebstormProjects/webpack2_config/node_modules/purifycss-webpack/dist/parse.js:20
    throw new Error('Failed to find ' + chunkName + ' in ' + paths.join(', '));
                                                                   ^

TypeError: paths.join is not a function
    at Object.parseEntries [as entries] (/home/jeggett/WebstormProjects/webpack2_config/node_modules/purifycss-webpack/dist/parse.js:20:68)
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/purifycss-webpack/dist/index.js:76:41
    at Array.forEach (native)
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/purifycss-webpack/dist/index.js:72:28
    at Array.forEach (native)
    at Compilation.<anonymous> (/home/jeggett/WebstormProjects/webpack2_config/node_modules/purifycss-webpack/dist/index.js:57:30)
    at next (/home/jeggett/WebstormProjects/webpack2_config/node_modules/tapable/lib/Tapable.js:140:14)
    at ExtractTextPlugin.<anonymous> (/home/jeggett/WebstormProjects/webpack2_config/node_modules/extract-text-webpack-plugin/index.js:314:4)
    at Compilation.applyPluginsAsyncSeries (/home/jeggett/WebstormProjects/webpack2_config/node_modules/tapable/lib/Tapable.js:142:13)
    at sealPart2 (/home/jeggett/WebstormProjects/webpack2_config/node_modules/webpack/lib/Compilation.js:597:9)
    at next (/home/jeggett/WebstormProjects/webpack2_config/node_modules/tapable/lib/Tapable.js:138:11)
    at ExtractTextPlugin.<anonymous> (/home/jeggett/WebstormProjects/webpack2_config/node_modules/extract-text-webpack-plugin/index.js:290:5)
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/async/dist/async.js:356:16
    at iteratorCallback (/home/jeggett/WebstormProjects/webpack2_config/node_modules/async/dist/async.js:936:13)
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/async/dist/async.js:840:16
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/extract-text-webpack-plugin/index.js:274:6
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/async/dist/async.js:356:16
    at iteratorCallback (/home/jeggett/WebstormProjects/webpack2_config/node_modules/async/dist/async.js:936:13)
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/async/dist/async.js:840:16
    at /home/jeggett/WebstormProjects/webpack2_config/node_modules/extract-text-webpack-plugin/index.js:264:9
    at rebuilding.forEach.cb (/home/jeggett/WebstormProjects/webpack2_config/node_modules/webpack/lib/Compilation.js:475:29)
    at Array.forEach (native)
    at callback (/home/jeggett/WebstormProjects/webpack2_config/node_modules/webpack/lib/Compilation.js:475:15)
    at processModuleDependencies (/home/jeggett/WebstormProjects/webpack2_config/node_modules/webpack/lib/Compilation.js:494:5)
    at _combinedTickCallback (internal/process/next_tick.js:67:7)
    at process._tickCallback (internal/process/next_tick.js:98:9)

Link to the project, purify-webpack v0.4.0, node v7.4.0. OS Kubuntu Linux 16.10

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