diff --git a/src/net/http/httptest/server.go b/src/net/http/httptest/server.go
index 1baec23d57..6075397a26 100644
--- a/src/net/http/httptest/server.go
+++ b/src/net/http/httptest/server.go
@@ -93,9 +93,6 @@ func NewUnstartedServer(handler http.Handler) *Server {
 	return &Server{
 		Listener: newLocalListener(),
 		Config:   &http.Server{Handler: handler},
-		client: &http.Client{
-			Transport: &http.Transport{},
-		},
 	}
 }
 
@@ -104,6 +101,9 @@ func (s *Server) Start() {
 	if s.URL != "" {
 		panic("Server already started")
 	}
+	if s.client == nil {
+		s.client = &http.Client{Transport: &http.Transport{}}
+	}
 	s.URL = "http://" + s.Listener.Addr().String()
 	s.wrap()
 	s.goServe()
@@ -118,6 +118,9 @@ func (s *Server) StartTLS() {
 	if s.URL != "" {
 		panic("Server already started")
 	}
+	if s.client == nil {
+		s.client = &http.Client{Transport: &http.Transport{}}
+	}
 	cert, err := tls.X509KeyPair(internal.LocalhostCert, internal.LocalhostKey)
 	if err != nil {
 		panic(fmt.Sprintf("httptest: NewTLSServer: %v", err))
diff --git a/src/net/http/httptest/server_test.go b/src/net/http/httptest/server_test.go
index d97cec5fdd..8ab50cdb0a 100644
--- a/src/net/http/httptest/server_test.go
+++ b/src/net/http/httptest/server_test.go
@@ -12,8 +12,48 @@ import (
 	"testing"
 )
 
+type newServerFunc func(http.Handler) *Server
+
+var newServers = map[string]newServerFunc{
+	"NewServer":    NewServer,
+	"NewTLSServer": NewTLSServer,
+
+	// The manual variants of newServer create a Server manually by only filling
+	// in the exported fields of Server.
+	"NewServerManual": func(h http.Handler) *Server {
+		ts := &Server{Listener: newLocalListener(), Config: &http.Server{Handler: h}}
+		ts.Start()
+		return ts
+	},
+	"NewTLSServerManual": func(h http.Handler) *Server {
+		ts := &Server{Listener: newLocalListener(), Config: &http.Server{Handler: h}}
+		ts.StartTLS()
+		return ts
+	},
+}
+
 func TestServer(t *testing.T) {
-	ts := NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	for _, name := range []string{"NewServer", "NewServerManual"} {
+		t.Run(name, func(t *testing.T) {
+			newServer := newServers[name]
+			t.Run("Server", func(t *testing.T) { testServer(t, newServer) })
+			t.Run("GetAfterClose", func(t *testing.T) { testGetAfterClose(t, newServer) })
+			t.Run("ServerCloseBlocking", func(t *testing.T) { testServerCloseBlocking(t, newServer) })
+			t.Run("ServerCloseClientConnections", func(t *testing.T) { testServerCloseClientConnections(t, newServer) })
+			t.Run("ServerClientTransportType", func(t *testing.T) { testServerClientTransportType(t, newServer) })
+		})
+	}
+	for _, name := range []string{"NewTLSServer", "NewTLSServerManual"} {
+		t.Run(name, func(t *testing.T) {
+			newServer := newServers[name]
+			t.Run("ServerClient", func(t *testing.T) { testServerClient(t, newServer) })
+			t.Run("TLSServerClientTransportType", func(t *testing.T) { testTLSServerClientTransportType(t, newServer) })
+		})
+	}
+}
+
+func testServer(t *testing.T, newServer newServerFunc) {
+	ts := newServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("hello"))
 	}))
 	defer ts.Close()
@@ -32,8 +72,8 @@ func TestServer(t *testing.T) {
 }
 
 // Issue 12781
-func TestGetAfterClose(t *testing.T) {
-	ts := NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+func testGetAfterClose(t *testing.T, newServer newServerFunc) {
+	ts := newServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("hello"))
 	}))
 
@@ -58,8 +98,8 @@ func TestGetAfterClose(t *testing.T) {
 	}
 }
 
-func TestServerCloseBlocking(t *testing.T) {
-	ts := NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+func testServerCloseBlocking(t *testing.T, newServer newServerFunc) {
+	ts := newServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("hello"))
 	}))
 	dial := func() net.Conn {
@@ -87,9 +127,9 @@ func TestServerCloseBlocking(t *testing.T) {
 }
 
 // Issue 14290
-func TestServerCloseClientConnections(t *testing.T) {
+func testServerCloseClientConnections(t *testing.T, newServer newServerFunc) {
 	var s *Server
-	s = NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	s = newServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		s.CloseClientConnections()
 	}))
 	defer s.Close()
@@ -102,8 +142,8 @@ func TestServerCloseClientConnections(t *testing.T) {
 
 // Tests that the Server.Client method works and returns an http.Client that can hit
 // NewTLSServer without cert warnings.
-func TestServerClient(t *testing.T) {
-	ts := NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+func testServerClient(t *testing.T, newTLSServer newServerFunc) {
+	ts := newTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("hello"))
 	}))
 	defer ts.Close()
@@ -124,8 +164,8 @@ func TestServerClient(t *testing.T) {
 
 // Tests that the Server.Client.Transport interface is implemented
 // by a *http.Transport.
-func TestServerClientTransportType(t *testing.T) {
-	ts := NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+func testServerClientTransportType(t *testing.T, newServer newServerFunc) {
+	ts := newServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 	}))
 	defer ts.Close()
 	client := ts.Client()
@@ -136,8 +176,8 @@ func TestServerClientTransportType(t *testing.T) {
 
 // Tests that the TLS Server.Client.Transport interface is implemented
 // by a *http.Transport.
-func TestTLSServerClientTransportType(t *testing.T) {
-	ts := NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+func testTLSServerClientTransportType(t *testing.T, newTLSServer newServerFunc) {
+	ts := newTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 	}))
 	defer ts.Close()
 	client := ts.Client()