diff --git a/upload/source/module/forum/forum_attachment.php b/upload/source/module/forum/forum_attachment.php
index e2ab564df717ce752fdb1381899a11e9e8b8d53e..354a3df62c131bc5f5c819ce31be3b743a7beb9f 100644
--- a/upload/source/module/forum/forum_attachment.php
+++ b/upload/source/module/forum/forum_attachment.php
@@ -333,7 +333,7 @@ function getlocalfile($filename, $readmod = 2, $range_start = 0, $range_end = 0)
 }
 
 function send_file_by_chunk($fp, $limit = PHP_INT_MAX) {
-	static $CHUNK_SIZE = 64 * 1024; // 每次最大读 64KB
+	static $CHUNK_SIZE = 65536; // 每次最大读 64KB
 	$count = 0;
 	while (!feof($fp)) {
 		$size_to_read = $CHUNK_SIZE;