Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 11731)
+++ wp-includes/formatting.php	(working copy)
@@ -2352,6 +2352,10 @@
 			$value = abs((int) $value);
 			break;
 
+		case 'users_can_register':
+			$value = (int) $value;
+			break;
+
 		case 'posts_per_page':
 		case 'posts_per_rss':
 			$value = (int) $value;