diff --git a/src/BookSearch/BookSearch.php b/src/BookSearch/BookSearch.php
index fad8d79..51e4d6e 100644
--- a/src/BookSearch/BookSearch.php
+++ b/src/BookSearch/BookSearch.php
@@ -179,6 +179,7 @@ class BookSearch
         $books = array();
         if(isset($results['response']['docs']) && is_array($results['response']['docs'])) {
             foreach($results['response']['docs'] as $r) {
+                if (!isset($r['id'])) continue;
                 $books[$r['id']] = $r;
             }
         }