diff --git i/src/net/http/httputil/reverseproxy.go w/src/net/http/httputil/reverseproxy.go
index 44d15ff..8c471a9 100644
--- i/src/net/http/httputil/reverseproxy.go
+++ w/src/net/http/httputil/reverseproxy.go
@@ -90,6 +90,11 @@ func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy {
        } else {
            req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
        }
+       if _, ok := req.Header["User-Agent"]; !ok {
+           // explicitly disable User-Agent so it's not set to
+           // default value
+           req.Header.Set("User-Agent", "")
+       }
    }
    return &ReverseProxy{Director: director}
 }
diff --git i/src/net/http/httputil/reverseproxy_test.go w/src/net/http/httputil/reverseproxy_test.go
index e9c0658..1065561 100644
--- i/src/net/http/httputil/reverseproxy_test.go
+++ w/src/net/http/httputil/reverseproxy_test.go
@@ -41,6 +41,9 @@ func TestReverseProxy(t *testing.T) {
        if len(r.TransferEncoding) > 0 {
            t.Errorf("backend got unexpected TransferEncoding: %v", r.TransferEncoding)
        }
+       if c := r.Header.Get("User-Agent"); c != "" {
+           t.Errorf("handler got User-Agent header value %q", c)
+       }
        if r.Header.Get("X-Forwarded-For") == "" {
            t.Errorf("didn't get X-Forwarded-For header")
        }
@@ -80,6 +83,7 @@ func TestReverseProxy(t *testing.T) {

    getReq, _ := http.NewRequest("GET", frontend.URL, nil)
    getReq.Host = "some-name"
+   getReq.Header.Set("User-Agent", "")
    getReq.Header.Set("Connection", "close")
    getReq.Header.Set("Proxy-Connection", "should be deleted")
    getReq.Header.Set("Upgrade", "foo")