diff --git a/wchat/common/HttpClient.php b/wchat/common/HttpClient.php
index 67f5409..0450c87 100644
--- a/wchat/common/HttpClient.php
+++ b/wchat/common/HttpClient.php
@@ -623,7 +623,7 @@ class HttpClient
 		if (is_array($body)) {
 			return $body;
 		}
-		$type = $data['content-type'];
+		$type = $data['content-type'] ?? 'text/html';
 		if (strpos($type, 'text/html') !== false) {
 			return $body;
 		} else if (strpos($type, 'json') !== false) {