diff --git a/message.go b/message.go
index 2ab2ee6..b14efbc 100644
--- a/message.go
+++ b/message.go
@@ -221,7 +221,7 @@ type Message struct {
 	// Inline keyboard attached to the message.
 	ReplyMarkup InlineKeyboardMarkup `json:"reply_markup"`
 
-	VoiceChatSchedule *VoiceChatSchedule `json:"voice_chat_scheduled,omitempty"`
+	VoiceChatSchedule *VoiceChatScheduled `json:"voice_chat_scheduled,omitempty"`
 
 	// For a service message, a voice chat started in the chat.
 	VoiceChatStarted *VoiceChatStarted `json:"voice_chat_started,omitempty"`
diff --git a/sendable.go b/sendable.go
index c843896..7047494 100644
--- a/sendable.go
+++ b/sendable.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"path/filepath"
 	"strconv"
+	"strings"
 )
 
 // Recipient is any possible endpoint you can send
@@ -345,7 +346,7 @@ func (i *Invoice) Send(b *Bot, to Recipient, opt *SendOptions) (*Message, error)
 		params["prices"] = string(data)
 	}
 	if len(i.SuggestedTipAmounts) > 0 {
-		params["suggested_tip_amounts"] = sliceIntToString(i.SuggestedTipAmounts)
+		params["suggested_tip_amounts"] = "[" + strings.Join(intsToStrs(i.SuggestedTipAmounts), ",") + "]"
 	}
 	b.embedSendOptions(params, opt)
 
diff --git a/util.go b/util.go
index 4c95b24..f316f12 100644
--- a/util.go
+++ b/util.go
@@ -252,10 +252,9 @@ func isUserInList(user *User, list []User) bool {
 	return false
 }
 
-func sliceIntToString(ns []int) (s string) {
+func intsToStrs(ns []int) (s []string) {
 	for _, n := range ns {
-		s += strconv.Itoa(n) + ","
+		s = append(s, strconv.Itoa(n))
 	}
-	s = s[:len(s)-1]
 	return
 }
diff --git a/voicechat.go b/voice.go
similarity index 69%
rename from voicechat.go
rename to voice.go
index 549b37d..7e8f967 100644
--- a/voicechat.go
+++ b/voice.go
@@ -18,12 +18,12 @@ type VoiceChatParticipantsInvited struct {
 	Users []User `json:"users"`
 }
 
-// VoiceChatSchedule represents a service message about a voice chat scheduled in the chat.
-type VoiceChatSchedule struct {
-	StartUnixTime int64 `json:"start_date"`
+// VoiceChatScheduled represents a service message about a voice chat scheduled in the chat.
+type VoiceChatScheduled struct {
+	Unixtime int64 `json:"start_date"`
 }
 
 // ExpireDate returns the point when the voice chat is supposed to be started by a chat administrator.
-func (v *VoiceChatSchedule) ExpireDate() time.Time {
-	return time.Unix(v.StartUnixTime, 0)
+func (v *VoiceChatScheduled) ExpireDate() time.Time {
+	return time.Unix(v.Unixtime, 0)
 }