Async responses with Aleph aren't being received over IPv4 but are with IPv6

Question

I'm trying to get server-sent events set up in Clojure with Aleph, but it's just not working over IPv4. Everything is fine if I connect over IPv6. This occurs both on Linux and MacOS. I've got a full example of what I'm talking about on GitHub.

I don't think I'm doing anything particularly fancy. The whole code is up on GitHub, but essentially my program is:

(def my-channel (permanent-channel))

(defroutes app-routes
  (GET "/events" []
    {:headers {"Content-Type" "text/event-stream"}
     :body my-channel}))

(def app
  (handler/site app-routes))

(start-server (wrap-ring-handler app) {:port 3000}))

However, when I connect to 127.0.0.1:3000, I can see curl sending the request headers, but it just hangs, never printing the response headers:

$ curl -vvv http://127.0.0.1:3000/events

* About to connect() to 127.0.0.1 port 3000 (#0)
*   Trying 127.0.0.1...
* Adding handle: conn: 0x7f920a004400
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x7f920a004400) send_pipe: 1, recv_pipe: 0
* Connected to 127.0.0.1 (127.0.0.1) port 3000 (#0)
> GET /events HTTP/1.1
> User-Agent: curl/7.30.0
> Host: 127.0.0.1:3000
> Accept: */*

If I connect over IPv6 the response comes right away, and events that I enqueue in the channel get sent correctly:

$ curl -vvv http://localhost:3000/events

* Adding handle: conn: 0x7f943c001a00
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x7f943c001a00) send_pipe: 1, recv_pipe: 0
* About to connect() to localhost port 3000 (#0)
*   Trying ::1...
* Connected to localhost (::1) port 3000 (#0)
> GET /events HTTP/1.1
> User-Agent: curl/7.30.0
> Host: localhost:3000
> Accept: */*
>
< HTTP/1.1 200 OK
* Server aleph/0.3.0 is not blacklisted
< Server: aleph/0.3.0
< Date: Tue, 15 Apr 2014 12:27:05 GMT
< Connection: keep-alive
< Content-Type: text/event-stream
< Transfer-Encoding: chunked

I have also reproduced this behaviour in Chrome. In both the IPv4 and IPv6 cases, tcpdump shows that the response headers are going over the wire.

This behaviour occurs both with lein run and an uberjar. It also occurs if I execute the uberjar with -Djava.net.preferIPv4Stack=true.

How do I get my application to behave the same over IPv4 as over IPv6?