The concat config lives in _octopress.yml which can be set to a different file with the --octopress-config option. That happens in the tests on line [170](https://github.com/octopress/ink/pull/10/files#diff-81f86f40f18ca5e6ba1943cb6f6ed4a3R170). Like I said, locally this runs fine. It's like somehow it doesn't load this configuration file on Travis.