diff --git a/include/functions.php b/include/functions.php
index 0e98b4a54..9edd2dd2c 100644
--- a/include/functions.php
+++ b/include/functions.php
@@ -4707,7 +4707,7 @@
 	}
 
 	function is_html($content) {
-		return preg_match("/<html|DOCTYPE html/i", $content) !== 0;
+		return preg_match("/<html|DOCTYPE html/i", substr($content, 0, 20)) !== 0;
 	}
 
 	function url_is_html($url, $login = false, $pass = false) {