diff --git a/wp-admin/admin-header.php b/wp-admin/admin-header.php
index f991c4cca..6db94218e 100644
--- a/wp-admin/admin-header.php
+++ b/wp-admin/admin-header.php
@@ -92,6 +92,7 @@ tinyMCE.init({
 	theme_advanced_toolbar_align : "left",
 	theme_advanced_path_location : "bottom",
 	theme_advanced_resizing : true,
+	theme_advanced_resize_horizontal : false,
 	entity_encoding : "raw",
 	extended_valid_elements : "a[id|href|title|onclick],img[class|src|alt|title|width|height|align]",
 	plugins : "emotions"