diff --git a/server/api/admin.go b/server/api/admin.go
index 1dddf57ba8f..9c33da1d5ab 100644
--- a/server/api/admin.go
+++ b/server/api/admin.go
@@ -59,13 +59,18 @@ func (h *adminHandler) ResetTS(w http.ResponseWriter, r *http.Request) {
 	if err := apiutil.ReadJSONRespondError(h.rd, w, r.Body, &input); err != nil {
 		return
 	}
-	ts, ok := input["tso"].(float64)
-	if !ok || ts < 0 {
+	tsValue, ok := input["tso"].(string)
+	if !ok || len(tsValue) == 0 {
+		h.rd.JSON(w, http.StatusBadRequest, "invalid tso value")
+		return
+	}
+	ts, err := strconv.ParseUint(tsValue, 10, 64)
+	if err != nil {
 		h.rd.JSON(w, http.StatusBadRequest, "invalid tso value")
 		return
 	}
 
-	if err := handler.ResetTS(uint64(ts)); err != nil {
+	if err = handler.ResetTS(ts); err != nil {
 		if err == server.ErrServerNotStarted {
 			h.rd.JSON(w, http.StatusInternalServerError, err.Error())
 		} else {
diff --git a/server/api/admin_test.go b/server/api/admin_test.go
index 9752d50318b..a6a8fbc4e2c 100644
--- a/server/api/admin_test.go
+++ b/server/api/admin_test.go
@@ -16,7 +16,6 @@ package api
 import (
 	"encoding/json"
 	"fmt"
-	"math"
 	"net/http"
 	"strings"
 	"time"
@@ -92,9 +91,9 @@ type testTSOSuite struct {
 	urlPrefix string
 }
 
-func makeTS(offset time.Duration) int64 {
+func makeTS(offset time.Duration) uint64 {
 	physical := time.Now().Add(offset).UnixNano() / int64(time.Millisecond)
-	return physical << 18
+	return uint64(physical << 18)
 }
 
 func (s *testTSOSuite) SetUpSuite(c *C) {
@@ -115,7 +114,7 @@ func (s *testTSOSuite) TestResetTS(c *C) {
 	args := make(map[string]interface{})
 	t1 := makeTS(time.Hour)
 	url := s.urlPrefix
-	args["tso"] = t1
+	args["tso"] = fmt.Sprintf("%d", t1)
 	values, err := json.Marshal(args)
 	c.Assert(err, IsNil)
 	err = postJSON(url, values,
@@ -126,7 +125,7 @@ func (s *testTSOSuite) TestResetTS(c *C) {
 
 	c.Assert(err, IsNil)
 	t2 := makeTS(32 * time.Hour)
-	args["tso"] = t2
+	args["tso"] = fmt.Sprintf("%d", t2)
 	values, err = json.Marshal(args)
 	c.Assert(err, IsNil)
 	err = postJSON(url, values,
@@ -135,7 +134,7 @@ func (s *testTSOSuite) TestResetTS(c *C) {
 	c.Assert(strings.Contains(err.Error(), "too large"), IsTrue)
 
 	t3 := makeTS(-2 * time.Hour)
-	args["tso"] = t3
+	args["tso"] = fmt.Sprintf("%d", t3)
 	values, err = json.Marshal(args)
 	c.Assert(err, IsNil)
 	err = postJSON(url, values,
@@ -143,8 +142,7 @@ func (s *testTSOSuite) TestResetTS(c *C) {
 	c.Assert(err, NotNil)
 	c.Assert(strings.Contains(err.Error(), "small"), IsTrue)
 
-	t4 := math.MinInt64
-	args["tso"] = t4
+	args["tso"] = ""
 	values, err = json.Marshal(args)
 	c.Assert(err, IsNil)
 	err = postJSON(url, values,
@@ -152,4 +150,11 @@ func (s *testTSOSuite) TestResetTS(c *C) {
 	c.Assert(err, NotNil)
 	c.Assert(err.Error(), Equals, "\"invalid tso value\"\n")
 
+	args["tso"] = "test"
+	values, err = json.Marshal(args)
+	c.Assert(err, IsNil)
+	err = postJSON(url, values,
+		func(_ []byte, code int) { c.Assert(code, Equals, http.StatusBadRequest) })
+	c.Assert(err, NotNil)
+	c.Assert(err.Error(), Equals, "\"invalid tso value\"\n")
 }