Getting "java.lang.Exception: Unrecognized body" when using ring-json on heroku

I'm using ring-json to deliver json data to a front end that uses reagent to render some d3 charts. I've had the simple project working locally, but when I deployed it to heroku I got the following errors (from the heroku log):


2016-08-01T15:50:38.955857+00:00 app[web.1]: java.lang.Exception: Unrecognized body: [{:key "GB", :values [{:y 2.4555984, :x 2002} {:y 2.519768, :x 2004} {:y 2.4532163, :x 2006} {:y 2.420068, :x 2008} {:y 2.464492, :x 2010} {:y 2.321085, :x 2012}]} {:key "ES", :values [{:y 2.2434933, :x 2002} {:y 2.34095, :x 2004} {:y 2.1764393, :x 2006} {:y 2.0458074, :x 2008} {:y 2.1055703, :x 2010} {:y 2.041821, :x 2012}]} {:key "DE", :values [{:y 2.3088598, :x 2002} {:y 2.3240418, :x 2004} {:y 2.414952, :x 2006} {:y 2.2453654, :x 2008} {:y 2.2269878, :x 2010} {:y 2.1301556, :x 2012}]} {:key "FR", :values [{:y 2.292432, :x 2002} {:y 2.6937985, :x 2004} {:y 2.2779455, :x 2006} {:y 2.3077664, :x 2008} {:y 2.390625, :x 2010} {:y 2.3109756, :x 2012}]} {:key "HU", :values [{:y 2.5220544, :x 2002} {:y 2.570761, :x 2004} {:y 2.7397892, :x 2006} {:y 3.0420985, :x 2008} {:y 2.8456118, :x 2010} {:y 2.5978153, :x 2012}]} {:key "FI", :values [{:y 2.3738055, :x 2002} {:y 2.4264107, :x 2004} {:y 3.1687763, :x 2006} {:y 3.2200456, :x 2008} {:y 3.2385516, :x 2010} {:y 2.240783, :x 2012}]} {:key "PT", :values [{:y 2.8570483, :x 2002} {:y 2.8615985, :x 2004} {:y 2.649865, :x 2006} {:y 2.7748206, :x 2008} {:y 2.8316278, :x 2010} {:y 2.8707578, :x 2012}]} {:key "SE", :values [{:y 2.7565827, :x 2002} {:y 2.7382352, :x 2004} {:y 3.7057602, :x 2006} {:y 3.5786886, :x 2008} {:y 2.478958, :x 2010} {:y 2.2799134, :x 2012}]}]
2016-08-01T15:50:38.955860+00:00 app[web.1]:    at ring.util.servlet$update_servlet_response.invokeStatic(servlet.clj:115)
2016-08-01T15:50:38.955859+00:00 app[web.1]:    at ring.util.servlet$set_body.invoke(servlet.clj:84)
2016-08-01T15:50:38.955861+00:00 app[web.1]:    at ring.adapter.jetty$proxy_handler$fn__3274.invoke(jetty.clj:26)
2016-08-01T15:50:38.955861+00:00 app[web.1]:    at ring.util.servlet$update_servlet_response.invoke(servlet.clj:107)
2016-08-01T15:50:38.955863+00:00 app[web.1]:    at ring.adapter.jetty.proxy$org.eclipse.jetty.server.handler.AbstractHandler$ff19274a.handle(Unknown Source)
2016-08-01T15:50:38.955865+00:00 app[web.1]:    at org.eclipse.jetty.server.Server.handle(Server.java:497)
2016-08-01T15:50:38.955858+00:00 app[web.1]:    at ring.util.servlet$set_body.invokeStatic(servlet.clj:105)
2016-08-01T15:50:38.955864+00:00 app[web.1]:    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
2016-08-01T15:50:38.955867+00:00 app[web.1]:    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
2016-08-01T15:50:38.955869+00:00 app[web.1]:    at java.lang.Thread.run(Thread.java:745)
2016-08-01T15:50:38.955866+00:00 app[web.1]:    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
2016-08-01T15:50:38.955868+00:00 app[web.1]:    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
2016-08-01T15:50:38.955866+00:00 app[web.1]:    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
2016-08-01T15:50:38.955865+00:00 app[web.1]:    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)

I'm not sure where to begin with this. Nor am I certain that it is a problem with ring-json. Do I perhaps need to set the headers somewhere? Any help would be greatly appreciated. Temporarily, here is a link to the project running on heroku: https://warm-dusk-72249.herokuapp.com/ . The project itself can be found at http://github.com/ezmiller/esd-viz.

ring-clojure / ring-json

Getting "java.lang.Exception: Unrecognized body" when using ring-json on heroku #44