diff --git a/mobile.netbiblio.php b/mobile.netbiblio.php
index 80b1186..ebfe333 100644
--- a/mobile.netbiblio.php
+++ b/mobile.netbiblio.php
@@ -323,9 +323,10 @@ class NetBiblio extends WebService
 
             if(count($files) > 0) {
                 foreach($booksWithoutFiles as $k => $b) {
-                    if(isset($files[$b['code']])) {
-                        $books[$k]['files'] = $files[$b['code']];
-                        $files[$b['code']]['id'] = $b['id'];
+                    $fileCode = sprintf("%05u", $b['code']);
+                    if(isset($files[$fileCode])) {
+                        $books[$k]['files'] = $files[$fileCode];
+                        $files[$fileCode]['id'] = $b['id'];
                     } else {
                         // we need to have an empty array for mobile apps compatibility.
                         $books[$k]['files'] = array();