diff --git a/configs.go b/configs.go
index aff0cd9..8b07982 100644
--- a/configs.go
+++ b/configs.go
@@ -474,6 +474,9 @@ func (config VoiceConfig) values() (url.Values, error) {
 	if config.Duration != 0 {
 		v.Add("duration", strconv.Itoa(config.Duration))
 	}
+	if config.Caption != "" {
+		v.Add("caption", config.Caption)
+	}
 
 	return v, nil
 }
@@ -485,6 +488,9 @@ func (config VoiceConfig) params() (map[string]string, error) {
 	if config.Duration != 0 {
 		params["duration"] = strconv.Itoa(config.Duration)
 	}
+	if config.Caption != "" {
+		params["caption"] = config.Caption
+	}
 
 	return params, nil
 }