diff --git a/book.php b/book.php
index 931997b..ed5aab0 100644
--- a/book.php
+++ b/book.php
@@ -166,6 +166,17 @@ class Book extends Base {
         return $this->datas;
     }
     
+    public function getDataById ($idData)
+    {
+        foreach ($this->getDatas () as $data) {
+            if ($data->id == $idData) {
+                return $data;
+            }
+        }
+        return NULL;
+    }
+
+    
     public function getTagsName () {
         $tagList = null;
         foreach ($this->getTags () as $tag) {
@@ -230,14 +241,8 @@ class Book extends Base {
         }
         else
         {
-            $result = parent::getDb ()->prepare('select format, name
-    from data where id = ?');
-            $result->execute (array ($idData));
-            
-            while ($post = $result->fetchObject ())
-            {
-                $file = $post->name . "." . strtolower ($post->format);
-            }
+            $data = $this->getDataById ($idData);
+            $file = $data->name . "." . strtolower ($data->format);
         }
 
         if ($relative)
@@ -340,13 +345,16 @@ where books.id = ?');
     }
     
     public static function getBookByDataId($dataId) {
-        $result = parent::getDb ()->prepare('select ' . self::BOOK_COLUMNS . '
+        $result = parent::getDb ()->prepare('select ' . self::BOOK_COLUMNS . ', data.name, data.format
 from data, books ' . self::SQL_BOOKS_LEFT_JOIN . '
 where data.book = books.id and data.id = ?');
         $result->execute (array ($dataId));
         while ($post = $result->fetchObject ())
         {
             $book = new Book ($post);
+            $data = new Data ($post, $book);
+            $data->id = $dataId;
+            $book->datas = array ($data);
             return $book;
         }
         return NULL;
diff --git a/data.php b/data.php
index 6869636..b66c8b6 100644
--- a/data.php
+++ b/data.php
@@ -58,7 +58,11 @@ class Data extends Base {
     }
     
     public function getMimeType () {
-        return self::$mimetypes [$this->extension];
+        if ($this->isKnownType ()) {
+            return self::$mimetypes [$this->extension];
+        } else {
+            return "application/octet-stream";
+        }
     }
     
     public function getFilename () {
diff --git a/fetch.php b/fetch.php
index cf60a68..4c8309b 100644
--- a/fetch.php
+++ b/fetch.php
@@ -87,7 +87,7 @@
             break;
     }
     $file = $book->getFilePath ($type, $idData, true);
-    header('Content-Type: application/octet-stream');
+    header('Content-Type: ' . $book->getDataById ($idData)->getMimeType ());
     header('Content-Disposition: attachment; filename="' . basename ($file) . '"');
     header ($config['cops_x_accel_redirect'] . ": " . $config['calibre_internal_directory'] . $file);
 ?>
\ No newline at end of file