diff --git a/pkg/legacygwjsonpb/marshal.go b/pkg/legacygwjsonpb/marshal.go
new file mode 100644
index 000000000000..eb9072ef966b
--- /dev/null
+++ b/pkg/legacygwjsonpb/marshal.go
@@ -0,0 +1,292 @@
+package legacygwjsonpb
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"reflect"
+
+	"github.com/golang/protobuf/jsonpb"
+	"github.com/golang/protobuf/proto"
+	gw "github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
+	protoV2 "google.golang.org/protobuf/proto"
+)
+
+// JSONPb is a Marshaler which marshals/unmarshals into/from JSON
+// with the "github.com/golang/protobuf/jsonpb".
+// It supports fully functionality of protobuf unlike JSONBuiltin.
+//
+// The NewDecoder method returns a DecoderWrapper, so the underlying
+// *json.Decoder methods can be used.
+type JSONPb jsonpb.Marshaler
+
+// ContentType always returns "application/json".
+func (*JSONPb) ContentType(v interface{}) string {
+	return "application/json"
+}
+
+// Marshal marshals "v" into JSON.
+func (j *JSONPb) Marshal(vv interface{}) (ret []byte, retErr error) {
+	var v interface{} = vv
+
+	// For unary api, the gateway always convert the messageV1 into V2.
+	// We should convert it back. And for the streaming api, the input is
+	// kind of map, we can't just call the proto.MessageV1 because it
+	// will panic :)
+	//
+	// REF: github.com/grpc-ecosystem/grpc-gateway/v2@v2.16.2/runtime/handler.goL75
+	if _, ok := vv.(protoV2.Message); ok {
+		v = proto.MessageV1(vv)
+	}
+
+	if _, ok := v.(proto.Message); !ok {
+		return j.marshalNonProtoField(v)
+	}
+
+	var buf bytes.Buffer
+	if err := j.marshalTo(&buf, v); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func (j *JSONPb) marshalTo(w io.Writer, v interface{}) error {
+	p, ok := v.(proto.Message)
+	if !ok {
+		buf, err := j.marshalNonProtoField(v)
+		if err != nil {
+			return err
+		}
+		_, err = w.Write(buf)
+		return err
+	}
+	return (*jsonpb.Marshaler)(j).Marshal(w, p)
+}
+
+var (
+	// protoMessageType is stored to prevent constant lookup of the same type at runtime.
+	protoMessageType = reflect.TypeOf((*proto.Message)(nil)).Elem()
+)
+
+// marshalNonProto marshals a non-message field of a protobuf message.
+// This function does not correctly marshals arbitrary data structure into JSON,
+// but it is only capable of marshaling non-message field values of protobuf,
+// i.e. primitive types, enums; pointers to primitives or enums; maps from
+// integer/string types to primitives/enums/pointers to messages.
+func (j *JSONPb) marshalNonProtoField(v interface{}) ([]byte, error) {
+	if v == nil {
+		return []byte("null"), nil
+	}
+	rv := reflect.ValueOf(v)
+	for rv.Kind() == reflect.Ptr {
+		if rv.IsNil() {
+			return []byte("null"), nil
+		}
+		rv = rv.Elem()
+	}
+
+	if rv.Kind() == reflect.Slice {
+		if rv.IsNil() {
+			if j.EmitDefaults {
+				return []byte("[]"), nil
+			}
+			return []byte("null"), nil
+		}
+
+		if rv.Type().Elem().Implements(protoMessageType) {
+			var buf bytes.Buffer
+			err := buf.WriteByte('[')
+			if err != nil {
+				return nil, err
+			}
+			for i := 0; i < rv.Len(); i++ {
+				if i != 0 {
+					err = buf.WriteByte(',')
+					if err != nil {
+						return nil, err
+					}
+				}
+				if err = (*jsonpb.Marshaler)(j).Marshal(&buf, rv.Index(i).Interface().(proto.Message)); err != nil {
+					return nil, err
+				}
+			}
+			err = buf.WriteByte(']')
+			if err != nil {
+				return nil, err
+			}
+
+			return buf.Bytes(), nil
+		}
+	}
+
+	if rv.Kind() == reflect.Map {
+		m := make(map[string]*json.RawMessage)
+		for _, k := range rv.MapKeys() {
+			buf, err := j.Marshal(rv.MapIndex(k).Interface())
+			if err != nil {
+				return nil, err
+			}
+			m[fmt.Sprintf("%v", k.Interface())] = (*json.RawMessage)(&buf)
+		}
+		if j.Indent != "" {
+			return json.MarshalIndent(m, "", j.Indent)
+		}
+		return json.Marshal(m)
+	}
+	if enum, ok := rv.Interface().(protoEnum); ok && !j.EnumsAsInts {
+		return json.Marshal(enum.String())
+	}
+	return json.Marshal(rv.Interface())
+}
+
+// Unmarshal unmarshals JSON "data" into "v"
+func (j *JSONPb) Unmarshal(data []byte, v interface{}) error {
+	return unmarshalJSONPb(data, v)
+}
+
+// NewDecoder returns a Decoder which reads JSON stream from "r".
+func (j *JSONPb) NewDecoder(r io.Reader) gw.Decoder {
+	d := json.NewDecoder(r)
+	return DecoderWrapper{Decoder: d}
+}
+
+// DecoderWrapper is a wrapper around a *json.Decoder that adds
+// support for protos to the Decode method.
+type DecoderWrapper struct {
+	*json.Decoder
+}
+
+// Decode wraps the embedded decoder's Decode method to support
+// protos using a jsonpb.Unmarshaler.
+func (d DecoderWrapper) Decode(v interface{}) error {
+	return decodeJSONPb(d.Decoder, v)
+}
+
+// NewEncoder returns an Encoder which writes JSON stream into "w".
+func (j *JSONPb) NewEncoder(w io.Writer) gw.Encoder {
+	return gw.EncoderFunc(func(vv interface{}) error {
+		v := proto.MessageV1(vv)
+
+		if err := j.marshalTo(w, v); err != nil {
+			return err
+		}
+		// mimic json.Encoder by adding a newline (makes output
+		// easier to read when it contains multiple encoded items)
+		_, err := w.Write(j.Delimiter())
+		return err
+	})
+}
+
+func unmarshalJSONPb(data []byte, v interface{}) error {
+	d := json.NewDecoder(bytes.NewReader(data))
+	return decodeJSONPb(d, v)
+}
+
+func decodeJSONPb(d *json.Decoder, v interface{}) error {
+	p, ok := v.(proto.Message)
+	if !ok {
+		return decodeNonProtoField(d, v)
+	}
+	unmarshaler := &jsonpb.Unmarshaler{AllowUnknownFields: allowUnknownFields}
+	return unmarshaler.UnmarshalNext(d, p)
+}
+
+func decodeNonProtoField(d *json.Decoder, v interface{}) error {
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr {
+		return fmt.Errorf("%T is not a pointer", v)
+	}
+	for rv.Kind() == reflect.Ptr {
+		if rv.IsNil() {
+			rv.Set(reflect.New(rv.Type().Elem()))
+		}
+		if rv.Type().ConvertibleTo(typeProtoMessage) {
+			unmarshaler := &jsonpb.Unmarshaler{AllowUnknownFields: allowUnknownFields}
+			return unmarshaler.UnmarshalNext(d, rv.Interface().(proto.Message))
+		}
+		rv = rv.Elem()
+	}
+	if rv.Kind() == reflect.Map {
+		if rv.IsNil() {
+			rv.Set(reflect.MakeMap(rv.Type()))
+		}
+		conv, ok := convFromType[rv.Type().Key().Kind()]
+		if !ok {
+			return fmt.Errorf("unsupported type of map field key: %v", rv.Type().Key())
+		}
+
+		m := make(map[string]*json.RawMessage)
+		if err := d.Decode(&m); err != nil {
+			return err
+		}
+		for k, v := range m {
+			result := conv.Call([]reflect.Value{reflect.ValueOf(k)})
+			if err := result[1].Interface(); err != nil {
+				return err.(error)
+			}
+			bk := result[0]
+			bv := reflect.New(rv.Type().Elem())
+			if err := unmarshalJSONPb([]byte(*v), bv.Interface()); err != nil {
+				return err
+			}
+			rv.SetMapIndex(bk, bv.Elem())
+		}
+		return nil
+	}
+	if _, ok := rv.Interface().(protoEnum); ok {
+		var repr interface{}
+		if err := d.Decode(&repr); err != nil {
+			return err
+		}
+		switch repr.(type) {
+		case string:
+			// TODO(yugui) Should use proto.StructProperties?
+			return fmt.Errorf("unmarshaling of symbolic enum %q not supported: %T", repr, rv.Interface())
+		case float64:
+			rv.Set(reflect.ValueOf(int32(repr.(float64))).Convert(rv.Type()))
+			return nil
+		default:
+			return fmt.Errorf("cannot assign %#v into Go type %T", repr, rv.Interface())
+		}
+	}
+	return d.Decode(v)
+}
+
+type protoEnum interface {
+	fmt.Stringer
+	EnumDescriptor() ([]byte, []int)
+}
+
+var typeProtoMessage = reflect.TypeOf((*proto.Message)(nil)).Elem()
+
+// Delimiter for newline encoded JSON streams.
+func (j *JSONPb) Delimiter() []byte {
+	return []byte("\n")
+}
+
+// allowUnknownFields helps not to return an error when the destination
+// is a struct and the input contains object keys which do not match any
+// non-ignored, exported fields in the destination.
+var allowUnknownFields = true
+
+// DisallowUnknownFields enables option in decoder (unmarshaller) to
+// return an error when it finds an unknown field. This function must be
+// called before using the JSON marshaller.
+func DisallowUnknownFields() {
+	allowUnknownFields = false
+}
+
+var (
+	convFromType = map[reflect.Kind]reflect.Value{
+		reflect.String:  reflect.ValueOf(gw.String),
+		reflect.Bool:    reflect.ValueOf(gw.Bool),
+		reflect.Float64: reflect.ValueOf(gw.Float64),
+		reflect.Float32: reflect.ValueOf(gw.Float32),
+		reflect.Int64:   reflect.ValueOf(gw.Int64),
+		reflect.Int32:   reflect.ValueOf(gw.Int32),
+		reflect.Uint64:  reflect.ValueOf(gw.Uint64),
+		reflect.Uint32:  reflect.ValueOf(gw.Uint32),
+		reflect.Slice:   reflect.ValueOf(gw.Bytes),
+	}
+)
diff --git a/scripts/test.sh b/scripts/test.sh
index c8c6550ffa68..3bb89e800605 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -171,12 +171,12 @@ function grpcproxy_pass {
 
 function grpcproxy_integration_pass {
   # shellcheck disable=SC2068
-  run_for_module "tests" go_test "./integration/..." "fail_fast" : -timeout=30m -tags cluster_proxy ${COMMON_TEST_FLAGS[@]:-} "$@"
+  run_for_module "tests" go_test "./integration/..." "fail_fast" : -timeout=30m -tags cluster_proxy ${COMMON_TEST_FLAGS[@]:-} ${RUN_ARG[@]:-} "$@"
 }
 
 function grpcproxy_e2e_pass {
   # shellcheck disable=SC2068
-  run_for_module "tests" go_test "./e2e" "fail_fast" : -timeout=30m -tags cluster_proxy ${COMMON_TEST_FLAGS[@]:-} "$@"
+  run_for_module "tests" go_test "./e2e" "fail_fast" : -timeout=30m -tags cluster_proxy ${COMMON_TEST_FLAGS[@]:-} ${RUN_ARG[@]:-} "$@"
 }
 
 ################# COVERAGE #####################################################
diff --git a/server/embed/serve.go b/server/embed/serve.go
index 85cd41989b93..48841a220a32 100644
--- a/server/embed/serve.go
+++ b/server/embed/serve.go
@@ -28,6 +28,7 @@ import (
 	"go.etcd.io/etcd/client/pkg/v3/transport"
 	"go.etcd.io/etcd/pkg/v3/debugutil"
 	"go.etcd.io/etcd/pkg/v3/httputil"
+	"go.etcd.io/etcd/pkg/v3/legacygwjsonpb"
 	"go.etcd.io/etcd/server/v3/config"
 	"go.etcd.io/etcd/server/v3/etcdserver"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/v3client"
@@ -301,7 +302,12 @@ func (sctx *serveCtx) registerGateway(dial func(ctx context.Context) (*grpc.Clie
 	if err != nil {
 		return nil, err
 	}
-	gwmux := gw.NewServeMux()
+
+	gwmux := gw.NewServeMux(
+		gw.WithMarshalerOption(gw.MIMEWildcard, &gw.HTTPBodyMarshaler{
+			Marshaler: &legacygwjsonpb.JSONPb{OrigName: true},
+		}),
+	)
 
 	handlers := []registerHandlerFunc{
 		etcdservergw.RegisterKVHandler,
diff --git a/tests/e2e/v3_curl_test.go b/tests/e2e/v3_curl_test.go
index 354e756eba9b..04047db5bd43 100644
--- a/tests/e2e/v3_curl_test.go
+++ b/tests/e2e/v3_curl_test.go
@@ -30,10 +30,9 @@ import (
 	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
 	"go.etcd.io/etcd/api/v3/v3rpc/rpctypes"
 	"go.etcd.io/etcd/client/pkg/v3/testutil"
+	"go.etcd.io/etcd/pkg/v3/legacygwjsonpb"
 	epb "go.etcd.io/etcd/server/v3/etcdserver/api/v3election/v3electionpb"
 	"go.etcd.io/etcd/tests/v3/framework/e2e"
-
-	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
 )
 
 var apiPrefix = []string{"/v3"}
@@ -168,7 +167,7 @@ func testV3CurlTxn(cx ctlCtx) {
 			},
 		},
 	}
-	m := &runtime.JSONPb{}
+	m := &legacygwjsonpb.JSONPb{}
 	jsonDat, jerr := m.Marshal(txn)
 	if jerr != nil {
 		cx.t.Fatal(jerr)
@@ -181,7 +180,7 @@ func testV3CurlTxn(cx ctlCtx) {
 
 	// was crashing etcd server
 	malformed := `{"compare":[{"result":0,"target":1,"key":"Zm9v","TargetUnion":null}],"success":[{"Request":{"RequestPut":{"key":"Zm9v","value":"YmFy"}}}]}`
-	if err := e2e.CURLPost(cx.epc, e2e.CURLReq{Endpoint: path.Join(p, "/kv/txn"), Value: malformed, Expected: "error"}); err != nil {
+	if err := e2e.CURLPost(cx.epc, e2e.CURLReq{Endpoint: path.Join(p, "/kv/txn"), Value: malformed, Expected: `"code":3,"message":"etcdserver: key not found"`}); err != nil {
 		cx.t.Fatalf("failed testV3CurlTxn put with curl using prefix (%s) (%v)", p, err)
 	}
 
@@ -232,7 +231,7 @@ func testV3CurlAuth(cx ctlCtx) {
 		testutil.AssertNil(cx.t, err)
 
 		// fail put no auth
-		if err = e2e.CURLPost(cx.epc, e2e.CURLReq{Endpoint: path.Join(p, "/kv/put"), Value: string(putreq), Expected: "error"}); err != nil {
+		if err = e2e.CURLPost(cx.epc, e2e.CURLReq{Endpoint: path.Join(p, "/kv/put"), Value: string(putreq), Expected: `"code":3,"message":"etcdserver: user name is empty"`}); err != nil {
 			cx.t.Fatalf("failed testV3CurlAuth no auth put with curl using prefix (%s) (%v)", p, err)
 		}
 
@@ -347,7 +346,7 @@ func testV3CurlProclaimMissiongLeaderKey(cx ctlCtx) {
 	if err = e2e.CURLPost(cx.epc, e2e.CURLReq{
 		Endpoint: path.Join(cx.apiPrefix, "/election/proclaim"),
 		Value:    string(pdata),
-		Expected: `{"error":"\"leader\" field must be provided","code":2,"message":"\"leader\" field must be provided"}`,
+		Expected: `{"code":2,"message":"\"leader\" field must be provided"}`,
 	}); err != nil {
 		cx.t.Fatalf("failed post proclaim request (%s) (%v)", cx.apiPrefix, err)
 	}
@@ -363,7 +362,7 @@ func testV3CurlResignMissiongLeaderKey(cx ctlCtx) {
 	if err := e2e.CURLPost(cx.epc, e2e.CURLReq{
 		Endpoint: path.Join(cx.apiPrefix, "/election/resign"),
 		Value:    `{}`,
-		Expected: `{"error":"\"leader\" field must be provided","code":2,"message":"\"leader\" field must be provided"}`,
+		Expected: `{"code":2,"message":"\"leader\" field must be provided"}`,
 	}); err != nil {
 		cx.t.Fatalf("failed post resign request (%s) (%v)", cx.apiPrefix, err)
 	}