Uglify to.js.liquid

So, I've used grunt-contrib-uglify in my workflow so far without any problems, but now I want my minicode to output to a .js.liquid file (it's for a Shopify project) which I haven't yet did it before.

I thought it would be simple, but when I run uglify job I get unexpected marker errors for any liquid tag instance in my source js files. Is there an argument I need to pass to uglify in order to complete the task?