diff --git a/app/vmctl/testdata/servers_integration_test/remote_write_server.go b/app/vmctl/testdata/servers_integration_test/remote_write_server.go
index cac2dfca0..ece2bde21 100644
--- a/app/vmctl/testdata/servers_integration_test/remote_write_server.go
+++ b/app/vmctl/testdata/servers_integration_test/remote_write_server.go
@@ -2,6 +2,7 @@ package remote_read_integration
 
 import (
 	"bufio"
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -10,6 +11,7 @@ import (
 	"reflect"
 	"sort"
 	"strconv"
+	"sync"
 	"testing"
 	"time"
 
@@ -169,14 +171,21 @@ func (rws *RemoteWriteServer) valuesHandler() http.Handler {
 			Data:   metricNames,
 		}
 
-		err := json.NewEncoder(w).Encode(resp)
+		buf := bytes.NewBuffer(nil)
+		err := json.NewEncoder(buf).Encode(resp)
 		if err != nil {
 			log.Printf("error send series: %s", err)
 			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
 
-		w.WriteHeader(http.StatusNoContent)
+		w.WriteHeader(http.StatusOK)
+		_, err = w.Write(buf.Bytes())
+		if err != nil {
+			log.Printf("error send series: %s", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
 		return
 	})
 }
@@ -191,7 +200,6 @@ func (rws *RemoteWriteServer) exportNativeHandler() http.Handler {
 			return
 		}
 
-		w.WriteHeader(http.StatusNoContent)
 		return
 	})
 }
@@ -202,6 +210,7 @@ func (rws *RemoteWriteServer) importNativeHandler(t *testing.T) http.Handler {
 		defer common.StopUnmarshalWorkers()
 
 		var gotTimeSeries []vm.TimeSeries
+		var mx sync.RWMutex
 
 		err := stream.Parse(r.Body, false, func(block *stream.Block) error {
 			mn := &block.MetricName
@@ -218,7 +227,9 @@ func (rws *RemoteWriteServer) importNativeHandler(t *testing.T) http.Handler {
 				})
 			}
 
+			mx.Lock()
 			gotTimeSeries = append(gotTimeSeries, timeseries)
+			mx.Unlock()
 
 			return nil
 		})
@@ -244,7 +255,8 @@ func (rws *RemoteWriteServer) importNativeHandler(t *testing.T) http.Handler {
 
 		if !reflect.DeepEqual(gotTimeSeries, rws.expectedSeries) {
 			w.WriteHeader(http.StatusInternalServerError)
-			t.Fatalf("datasets not equal, expected: %#v;\n got: %#v", rws.expectedSeries, gotTimeSeries)
+			t.Errorf("datasets not equal, expected: %#v;\n got: %#v", rws.expectedSeries, gotTimeSeries)
+			return
 		}
 
 		w.WriteHeader(http.StatusNoContent)