diff --git a/doc/go1.13.html b/doc/go1.13.html
index 3baf16c0af3..a17337f6662 100644
--- a/doc/go1.13.html
+++ b/doc/go1.13.html
@@ -821,7 +821,7 @@ godoc
     <p><!-- CL 154383 -->
       <a href="/pkg/net/http/#TimeoutHandler"><code>TimeoutHandler</code></a>'s
       <a href="/pkg/net/http/#ResponseWriter"><code>ResponseWriter</code></a> now implements the
-      <a href="/pkg/net/http/#Pusher"><code>Pusher</code></a> and <a href="/pkg/net/http/#Flusher"><code>Flusher</code></a> interfaces.
+      <a href="/pkg/net/http/#Pusher"><code>Pusher</code></a> interface.
     </p>
 
     <p><!-- CL 157339 -->
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 1d1449aa659..e86cc9bdd21 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -6161,6 +6161,54 @@ func TestUnsupportedTransferEncodingsReturn501(t *testing.T) {
 	}
 }
 
+// Issue 34439: ensure that TimeoutHandler doesn't implement Flusher
+// and that any interaction with Flusher won't affect TimeoutHandler's behavior.
+func TestTimeoutHandlerAndFlusher(t *testing.T) {
+	timeout := 50 * time.Millisecond
+
+	handler := HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.WriteHeader(StatusTeapot)
+		w.Write([]byte("line1\n"))
+		fl, ok := w.(Flusher)
+		if ok {
+			fl.Flush()
+		}
+		time.Sleep(timeout * 2)
+		w.Write([]byte("line2\n"))
+	})
+
+	cst := httptest.NewUnstartedServer(TimeoutHandler(handler, timeout, "TIMED OUT\n"))
+	// Provide a logger that will report an error on any superfluous log.
+	cst.Config.ErrorLog = log.New(&errorOnWrite{t: t}, "", 0)
+	cst.Start()
+	defer cst.Close()
+
+	res, err := cst.Client().Get(cst.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+
+	if g, w := res.StatusCode, StatusServiceUnavailable; g != w {
+		t.Errorf("Status code mismatch\ngot:  %d\nwant: %d", g, w)
+	}
+
+	slurp, _ := ioutil.ReadAll(res.Body)
+	if g, w := string(slurp), "TIMED OUT\n"; g != w {
+		t.Fatalf("Body mismatch\ngot:  %q\nwant: %q", g, w)
+	}
+}
+
+// errorOnWrite will invoke t.Error on any attempted write.
+type errorOnWrite struct {
+	t *testing.T
+}
+
+func (ew *errorOnWrite) Write(b []byte) (int, error) {
+	ew.t.Errorf("Unexpected write: %s\n", b)
+	return len(b), nil
+}
+
 // fetchWireResponse is a helper for dialing to host,
 // sending http1ReqBody as the payload and retrieving
 // the response as it was sent on the wire.
diff --git a/src/net/http/server.go b/src/net/http/server.go
index feff20045a0..9fd86ed7cd2 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -3272,7 +3272,6 @@ type timeoutWriter struct {
 }
 
 var _ Pusher = (*timeoutWriter)(nil)
-var _ Flusher = (*timeoutWriter)(nil)
 
 // Push implements the Pusher interface.
 func (tw *timeoutWriter) Push(target string, opts *PushOptions) error {
@@ -3282,14 +3281,6 @@ func (tw *timeoutWriter) Push(target string, opts *PushOptions) error {
 	return ErrNotSupported
 }
 
-// Flush implements the Flusher interface.
-func (tw *timeoutWriter) Flush() {
-	f, ok := tw.w.(Flusher)
-	if ok {
-		f.Flush()
-	}
-}
-
 func (tw *timeoutWriter) Header() Header { return tw.h }
 
 func (tw *timeoutWriter) Write(p []byte) (int, error) {