Index: wp-admin/includes/class-wp-upgrader.php
===================================================================
--- wp-admin/includes/class-wp-upgrader.php	(revision 20663)
+++ wp-admin/includes/class-wp-upgrader.php	(working copy)
@@ -1520,7 +1520,7 @@
 
 		$install_actions = array();
 		$install_actions['preview']  = '<a href="' . esc_url( $preview_link ) . '" class="hide-if-customize" title="' . esc_attr(sprintf(__('Preview &#8220;%s&#8221;'), $name ) ) . '">' . __('Preview') . '</a>';
-		$install_actions['preview'] .= '<a href="' . wp_customize_url( $stylesheet ) . '" class="hide-if-no-customize load-customize>' . __('Customize') . '</a>';
+		$install_actions['preview'] .= '<a href="' . wp_customize_url( $stylesheet ) . '" class="hide-if-no-customize load-customize">' . __('Customize') . '</a>';
 		$install_actions['activate'] = '<a href="' . esc_url( $activate_link ) . '" class="activatelink" title="' . esc_attr( sprintf( __('Activate &#8220;%s&#8221;'), $name ) ) . '">' . __('Activate') . '</a>';
 
 		if ( is_network_admin() && current_user_can( 'manage_network_themes' ) )