diff --git a/api/etemplate.php b/api/etemplate.php
index 478d0e5a6f..c5dd4ac56a 100644
--- a/api/etemplate.php
+++ b/api/etemplate.php
@@ -13,7 +13,7 @@
 use EGroupware\Api;
 
 // add et2- prefix to following widgets/tags
-const ADD_ET2_PREFIX_REGEXP = '#<((/?)([vh]?box|textbox|button))(/?|\s[^>]*)>#m';
+const ADD_ET2_PREFIX_REGEXP = '#<((/?)([vh]?box|textbox|textarea|button))(/?|\s[^>]*)>#m';
 
 // switch evtl. set output-compression off, as we cant calculate a Content-Length header with transparent compression
 ini_set('zlib.output_compression', 0);
@@ -64,6 +64,9 @@ function send_template()
 		// fix <menulist...><menupopup type="select-*"/></menulist> --> <select type="select-*" .../>
 		$str = preg_replace('#<menulist([^>]*)>[\r\n\s]*<menupopup([^>]+>)[\r\n\s]*</menulist>#', '<select$1$2', $str);
 
+		// fix <textbox multiline="true" .../> --> <textarea .../> (et2-prefix and self-closing is handled below)
+		$str = preg_replace('#<textbox(.*?)\smultiline="true"(.*?)/>#u', '<textarea$1$2/>', $str);
+
 		$str = preg_replace_callback(ADD_ET2_PREFIX_REGEXP, static function (array $matches)
 		{
 			return '<' . $matches[2] . 'et2-' . $matches[3] .