diff --git a/util/execdetails.go b/util/execdetails.go
index b3c377cec..b49298d21 100644
--- a/util/execdetails.go
+++ b/util/execdetails.go
@@ -635,7 +635,6 @@ func (td *TimeDetail) String() string {
 		return ""
 	}
 	buf := bytes.NewBuffer(make([]byte, 0, 16))
-	buf.WriteString("time_detail: {")
 	if td.ProcessTime > 0 {
 		buf.WriteString("total_process_time: ")
 		buf.WriteString(FormatDuration(td.ProcessTime))
diff --git a/util/misc_test.go b/util/misc_test.go
index ae819ac7f..304b70e22 100644
--- a/util/misc_test.go
+++ b/util/misc_test.go
@@ -88,3 +88,8 @@ func TestCompatibleParseGCTime(t *testing.T) {
 		assert.NotNil(err)
 	}
 }
+
+func TestTimeDetail(t *testing.T) {
+	detail := &TimeDetail{KvReadWallTime: time.Millisecond * 2, TotalRPCWallTime: time.Millisecond * 3}
+	assert.Equal(t, "time_detail: {total_kv_read_wall_time: 2ms, tikv_wall_time: 3ms}", detail.String())
+}