diff --git a/bot.go b/bot.go
index 5de8a93..bfd33d5 100644
--- a/bot.go
+++ b/bot.go
@@ -42,11 +42,11 @@ func botHello(m *tb.Message) (string, error) {
 	fmt.Println("botHello :", m.Text)
 	if !m.Private() {
 		fmt.Println("botHello : !m.Private()")
-		return
+		return ``, nil
 	}
 	//	fmt.Println("Hello payload :", m.Payload) // <PAYLOAD>
 	PrintText(m)
-	return "hello world", nil
+	return `hello world`, nil
 }
 
 func botChannelPost(m *tb.Message) {