Index: update-core.php
===================================================================
--- update-core.php	(revision 18444)
+++ update-core.php	(working copy)
@@ -66,7 +66,7 @@
 	echo '<input name="locale" value="'. esc_attr($update->locale) .'" type="hidden"/>';
 	if ( $show_buttons ) {
 		if ( $first_pass ) {
-			submit_button( $submit, 'button button-primary', 'upgrade', false );
+			submit_button( $submit, 'button'.((!$current)?' button-primary':''), 'upgrade', false );
 			$first_pass = false;
 		} else {
 			submit_button( $submit, 'button', 'upgrade', false );