Index: wp-admin/css/themes.css
===================================================================
--- wp-admin/css/themes.css	(revision 40747)
+++ wp-admin/css/themes.css	(working copy)
@@ -1068,7 +1068,7 @@
 	border: 1px solid #e5e5e5;
 	padding: 30px;
 	margin: 30px auto;
-	max-width: 380px;
+	max-width: 400px;
 }
 .upload-theme .install-help,
 .upload-plugin .install-help {