Edit your cljsbuild compiler options and add a source map output location. Wherever you put it, it needs to be accessible by the browser
:cljsbuild {:test-commands {"unit-tests" ["runners/phantomjs.js"
"resources/public/js/vendor/handlebars-1.0.rc.1.min.js"
"resources/private/js/unit-test.js"]}
:builds
[{:source-paths ["src/cljs"],
:id "dev",
:compiler {:pretty-print true,
:output-dir "resources/public/js/bin-debug",