Index: wp-admin/includes/class-wp-ms-sites-list-table.php
===================================================================
--- wp-admin/includes/class-wp-ms-sites-list-table.php	(revision 17488)
+++ wp-admin/includes/class-wp-ms-sites-list-table.php	(working copy)
@@ -72,7 +72,7 @@
 				$query .= " AND ( {$wpdb->blogs}.domain LIKE '$blog_s' ) ";
 			} else {
 				if ( $like_s != trim('/', $current_site->path) )
-					$blog_s = $current_site->path .= $like_s . $wild . '/';
+					$blog_s = $current_site->path . $like_s . $wild . '/';
 				else
 					$blog_s = $like_s;
 				$query .= " AND  ( {$wpdb->blogs}.path LIKE '$blog_s' )";