Index: nav-menu.php
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--- nav-menu.php	(revision 19587)
+++ nav-menu.php	(working copy)

@@ -584,7 +585,7 @@
 	$post_type_name = $post_type['args']->name;
 
 	// paginate browsing for large numbers of post objects
-	$per_page = 50;
+	$per_page = apply_filters( 'wp_nav_menu_item_post_type_per_page' , 50);
 	$pagenum = isset( $_REQUEST[$post_type_name . '-tab'] ) && isset( $_REQUEST['paged'] ) ? absint( $_REQUEST['paged'] ) : 1;
 	$offset = 0 < $pagenum ? $per_page * ( $pagenum - 1 ) : 0;