Index: wp-content/themes/twentyten/functions.php
===================================================================
--- wp-content/themes/twentyten/functions.php	(revision 22350)
+++ wp-content/themes/twentyten/functions.php	(working copy)
@@ -224,7 +224,8 @@
  * @since Twenty Ten 1.0
  */
 function twentyten_page_menu_args( $args ) {
-	$args['show_home'] = true;
+	if ( ! isset( $args['show_home'] ) )
+		$args['show_home'] = true;
 	return $args;
 }
 add_filter( 'wp_page_menu_args', 'twentyten_page_menu_args' );
Index: wp-content/themes/twentyeleven/functions.php
===================================================================
--- wp-content/themes/twentyeleven/functions.php	(revision 22350)
+++ wp-content/themes/twentyeleven/functions.php	(working copy)
@@ -375,7 +375,8 @@
  * Get our wp_nav_menu() fallback, wp_page_menu(), to show a home link.
  */
 function twentyeleven_page_menu_args( $args ) {
-	$args['show_home'] = true;
+	if ( ! isset( $args['show_home'] ) )
+		$args['show_home'] = true;
 	return $args;
 }
 add_filter( 'wp_page_menu_args', 'twentyeleven_page_menu_args' );
Index: wp-content/themes/twentytwelve/functions.php
===================================================================
--- wp-content/themes/twentytwelve/functions.php	(revision 22350)
+++ wp-content/themes/twentytwelve/functions.php	(working copy)
@@ -190,7 +190,8 @@
  * @since Twenty Twelve 1.0
  */
 function twentytwelve_page_menu_args( $args ) {
-	$args['show_home'] = true;
+	if ( ! isset( $args['show_home'] ) )
+		$args['show_home'] = true;
 	return $args;
 }
 add_filter( 'wp_page_menu_args', 'twentytwelve_page_menu_args' );