diff --git a/wp-admin/includes/class-wp-theme-install-list-table.php b/wp-admin/includes/class-wp-theme-install-list-table.php
index 412fe620e..ff9819219 100644
--- a/wp-admin/includes/class-wp-theme-install-list-table.php
+++ b/wp-admin/includes/class-wp-theme-install-list-table.php
@@ -275,10 +275,6 @@ class WP_Theme_Install_List_Table extends WP_Themes_List_Table {
 	 * @param object $theme - A WordPress.org Theme API object.
 	 */
 	function theme_installer_single( $theme ) {
-		$class = 'wp-full-overlay';
-		if ( $theme )
-			$class .= ' single-theme';
-
 		?>
 		<div id="theme-installer" class="wp-full-overlay single-theme">
 			<div class="wp-full-overlay-sidebar">
diff --git a/wp-admin/includes/theme-install.php b/wp-admin/includes/theme-install.php
index 253f5840e..1fdafec83 100644
--- a/wp-admin/includes/theme-install.php
+++ b/wp-admin/includes/theme-install.php
@@ -168,6 +168,9 @@ function install_theme_information() {
 	if ( is_wp_error( $theme ) )
 		wp_die( $theme );
 
+	iframe_header( __('Theme Install') );
 	$wp_list_table->theme_installer_single( $theme );
+	iframe_footer();
+	exit;
 }
 add_action('install_themes_pre_theme-information', 'install_theme_information');