diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index 95b6df5b6e..fdf820c380 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -50,7 +50,7 @@ function get_blogs_of_user( $id, $all = false ) {
 
 	$blogs = $match = array();
 	foreach ( (array) $user as $key => $value ) {
-		if ( false !== strpos( $key, '_capabilities') && 0 === strpos( $key, $wpdb->base_prefix ) && preg_match( '/' . $wpdb->base_prefix . '((\d+)_)?capabilities/', $key, $match ) ) {
+		if ( false !== strpos( $key, '_capabilities') && ( strlen( $wpdb->base_prefix ) == 0 || 0 === strpos( $key, $wpdb->base_prefix ) ) && preg_match( '/' . $wpdb->base_prefix . '((\d+)_)?capabilities/', $key, $match ) ) {
 			if ( count( $match ) > 2 )
 				$blog_id = $match[ 2 ];
 			else