diff --git a/wchat/common/HttpClient.php b/wchat/common/HttpClient.php
index d3f760b..d44322e 100644
--- a/wchat/common/HttpClient.php
+++ b/wchat/common/HttpClient.php
@@ -625,6 +625,7 @@ class HttpClient
 	{
 		try {
 			$this->method = self::POST;
+			$this->addHeader('Content-Type', 'multipart/form-data;charset=UTF-8');
 			$output = $this->curlParse($url, $params);
 			if ($output === FALSE) {
 				return new Result(['code' => 500, 'message' => $output]);