diff --git a/src/pkg/net/http/httputil/reverseproxy.go b/src/pkg/net/http/httputil/reverseproxy.go
index 9c4bd6e09a..2f08a8c0c9 100644
--- a/src/pkg/net/http/httputil/reverseproxy.go
+++ b/src/pkg/net/http/httputil/reverseproxy.go
@@ -17,6 +17,10 @@ import (
 	"time"
 )
 
+// beforeCopyResponse is a callback set by tests to intercept the state of the
+// output io.Writer before the data is copied to it.
+var beforeCopyResponse func(dst io.Writer)
+
 // ReverseProxy is an HTTP Handler that takes an incoming request and
 // sends it to another server, proxying the response back to the
 // client.
@@ -112,20 +116,32 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		rw.WriteHeader(http.StatusInternalServerError)
 		return
 	}
+	defer res.Body.Close()
 
 	copyHeader(rw.Header(), res.Header)
 
 	rw.WriteHeader(res.StatusCode)
+	p.copyResponse(rw, res.Body)
+}
 
-	if res.Body != nil {
-		var dst io.Writer = rw
-		if p.FlushInterval != 0 {
-			if wf, ok := rw.(writeFlusher); ok {
-				dst = &maxLatencyWriter{dst: wf, latency: p.FlushInterval}
+func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader) {
+	if p.FlushInterval != 0 {
+		if wf, ok := dst.(writeFlusher); ok {
+			mlw := &maxLatencyWriter{
+				dst:     wf,
+				latency: p.FlushInterval,
+				done:    make(chan bool),
 			}
+			go mlw.flushLoop()
+			defer mlw.stop()
+			dst = mlw
 		}
-		io.Copy(dst, res.Body)
 	}
+
+	if beforeCopyResponse != nil {
+		beforeCopyResponse(dst)
+	}
+	io.Copy(dst, src)
 }
 
 type writeFlusher interface {
@@ -137,22 +153,14 @@ type maxLatencyWriter struct {
 	dst     writeFlusher
 	latency time.Duration
 
-	lk   sync.Mutex // protects init of done, as well Write + Flush
+	lk   sync.Mutex // protects Write + Flush
 	done chan bool
 }
 
-func (m *maxLatencyWriter) Write(p []byte) (n int, err error) {
+func (m *maxLatencyWriter) Write(p []byte) (int, error) {
 	m.lk.Lock()
 	defer m.lk.Unlock()
-	if m.done == nil {
-		m.done = make(chan bool)
-		go m.flushLoop()
-	}
-	n, err = m.dst.Write(p)
-	if err != nil {
-		m.done <- true
-	}
-	return
+	return m.dst.Write(p)
 }
 
 func (m *maxLatencyWriter) flushLoop() {
@@ -160,13 +168,15 @@ func (m *maxLatencyWriter) flushLoop() {
 	defer t.Stop()
 	for {
 		select {
+		case <-m.done:
+			return
 		case <-t.C:
 			m.lk.Lock()
 			m.dst.Flush()
 			m.lk.Unlock()
-		case <-m.done:
-			return
 		}
 	}
 	panic("unreached")
 }
+
+func (m *maxLatencyWriter) stop() { m.done <- true }
diff --git a/src/pkg/net/http/httputil/reverseproxy_test.go b/src/pkg/net/http/httputil/reverseproxy_test.go
index 28e9c90ad3..3bcb23c077 100644
--- a/src/pkg/net/http/httputil/reverseproxy_test.go
+++ b/src/pkg/net/http/httputil/reverseproxy_test.go
@@ -7,11 +7,14 @@
 package httputil
 
 import (
+	"io"
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"runtime"
 	"testing"
+	"time"
 )
 
 func TestReverseProxy(t *testing.T) {
@@ -107,3 +110,58 @@ func TestReverseProxyQuery(t *testing.T) {
 		frontend.Close()
 	}
 }
+
+func TestReverseProxyFlushInterval(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+
+	const expected = "hi"
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(expected))
+	}))
+	defer backend.Close()
+
+	backendURL, err := url.Parse(backend.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	proxyHandler := NewSingleHostReverseProxy(backendURL)
+	proxyHandler.FlushInterval = time.Microsecond
+
+	dstChan := make(chan io.Writer, 1)
+	beforeCopyResponse = func(dst io.Writer) { dstChan <- dst }
+	defer func() { beforeCopyResponse = nil }()
+
+	frontend := httptest.NewServer(proxyHandler)
+	defer frontend.Close()
+
+	initGoroutines := runtime.NumGoroutine()
+	for i := 0; i < 100; i++ {
+		req, _ := http.NewRequest("GET", frontend.URL, nil)
+		req.Close = true
+		res, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("Get: %v", err)
+		}
+		if bodyBytes, _ := ioutil.ReadAll(res.Body); string(bodyBytes) != expected {
+			t.Errorf("got body %q; expected %q", bodyBytes, expected)
+		}
+
+		select {
+		case dst := <-dstChan:
+			if _, ok := dst.(*maxLatencyWriter); !ok {
+				t.Errorf("got writer %T; expected %T", dst, &maxLatencyWriter{})
+			}
+		default:
+			t.Error("maxLatencyWriter Write() was never called")
+		}
+
+		res.Body.Close()
+	}
+	// Allow up to 50 additional goroutines over 100 requests.
+	if delta := runtime.NumGoroutine() - initGoroutines; delta > 50 {
+		t.Errorf("grew %d goroutines; leak?", delta)
+	}
+}