diff --git a/src/net/http/h2_bundle.go b/src/net/http/h2_bundle.go
index 9a722e752ae..d6e749f8cda 100644
--- a/src/net/http/h2_bundle.go
+++ b/src/net/http/h2_bundle.go
@@ -3585,7 +3585,23 @@ func (sew http2stickyErrWriter) Write(p []byte) (n int, err error) {
 	return
 }
 
+var http2ErrNoCachedConn = errors.New("http2: no cached connection was available")
+
+// RoundTripOpt are options for the Transport.RoundTripOpt method.
+type http2RoundTripOpt struct {
+	// OnlyCachedConn controls whether RoundTripOpt may
+	// create a new TCP connection. If set true and
+	// no cached connection is available, RoundTripOpt
+	// will return ErrNoCachedConn.
+	OnlyCachedConn bool
+}
+
 func (t *http2Transport) RoundTrip(req *Request) (*Response, error) {
+	return t.RoundTripOpt(req, http2RoundTripOpt{})
+}
+
+// RoundTripOpt is like RoundTrip, but takes options.
+func (t *http2Transport) RoundTripOpt(req *Request, opt http2RoundTripOpt) (*Response, error) {
 	if req.URL.Scheme != "https" {
 		return nil, errors.New("http2: unsupported scheme")
 	}
@@ -3597,7 +3613,7 @@ func (t *http2Transport) RoundTrip(req *Request) (*Response, error) {
 	}
 
 	for {
-		cc, err := t.getClientConn(host, port)
+		cc, err := t.getClientConn(host, port, opt.OnlyCachedConn)
 		if err != nil {
 			return nil, err
 		}
@@ -3692,7 +3708,7 @@ func (t *http2Transport) addConn(key string, cc *http2clientConn) {
 	t.conns[key] = append(t.conns[key], cc)
 }
 
-func (t *http2Transport) getClientConn(host, port string) (*http2clientConn, error) {
+func (t *http2Transport) getClientConn(host, port string, onlyCached bool) (*http2clientConn, error) {
 	key := net.JoinHostPort(host, port)
 
 	t.connMu.Lock()
@@ -3703,6 +3719,9 @@ func (t *http2Transport) getClientConn(host, port string) (*http2clientConn, err
 		}
 	}
 	t.connMu.Unlock()
+	if onlyCached {
+		return nil, http2ErrNoCachedConn
+	}
 
 	cc, err := t.dialClientConn(host, port, key)
 	if err != nil {
diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index ad8aa19c2e4..809f6de2892 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -44,23 +44,21 @@ var DefaultTransport RoundTripper = &Transport{
 	ExpectContinueTimeout: 1 * time.Second,
 }
 
+// Wire up HTTP/2 support to the DefaultTransport, unless GODEBUG=h2client=0.
 func init() {
-	// TODO(bradfitz,adg): remove the following line before Go 1.6
-	// ships.  This just gives us a mechanism to temporarily
-	// enable the http2 client during development.
-	if !strings.Contains(os.Getenv("GODEBUG"), "h2client=1") {
+	if strings.Contains(os.Getenv("GODEBUG"), "h2client=0") {
 		return
 	}
-
 	t := DefaultTransport.(*Transport)
-
-	// TODO(bradfitz,adg): move all this up to DefaultTransport before Go 1.6:
 	t.RegisterProtocol("https", noDialH2Transport{h2DefaultTransport})
 	t.TLSClientConfig = &tls.Config{
 		NextProtos: []string{"h2"},
 	}
 	t.TLSNextProto = map[string]func(string, *tls.Conn) RoundTripper{
-		"h2": http2TransportForConn,
+		"h2": func(authority string, c *tls.Conn) RoundTripper {
+			h2DefaultTransport.AddIdleConn(authority, c)
+			return h2DefaultTransport
+		},
 	}
 }
 
@@ -69,14 +67,11 @@ func init() {
 type noDialH2Transport struct{ rt *http2Transport }
 
 func (t noDialH2Transport) RoundTrip(req *Request) (*Response, error) {
-	// TODO(bradfitz): wire up http2.Transport
-	return nil, ErrSkipAltProtocol
-}
-
-func http2TransportForConn(authority string, c *tls.Conn) RoundTripper {
-	// TODO(bradfitz): donate c to h2DefaultTransport:
-	// h2DefaultTransport.AddIdleConn(authority, c)
-	return h2DefaultTransport
+	res, err := t.rt.RoundTripOpt(req, http2RoundTripOpt{OnlyCachedConn: true})
+	if err == http2ErrNoCachedConn {
+		return nil, ErrSkipAltProtocol
+	}
+	return res, err
 }
 
 // DefaultMaxIdleConnsPerHost is the default value of Transport's