diff --git a/src/BookSearch/BookSearch.php b/src/BookSearch/BookSearch.php
index fb75786..69fba4e 100644
--- a/src/BookSearch/BookSearch.php
+++ b/src/BookSearch/BookSearch.php
@@ -295,7 +295,7 @@ class BookSearch
         $books = [];
         foreach($parts as $p) {
             // if we use array_merge here the numerical keys (book code) will be lost
-            $bs->addOrQuery($codes, $field);
+            $bs->addOrQuery($p, $field);
             $results = $bs->getResults(0, $count);
             $foundBooks = $results['books'];
             $books += $foundBooks;