diff --git a/base.php b/base.php
index 4a94cc1..7af0592 100644
--- a/base.php
+++ b/base.php
@@ -1072,6 +1072,13 @@ abstract class Base
         return is_array ($config['calibre_directory']);
     }
 
+    public static function useAbsolutePath () {
+        global $config;
+        $path = self::getDbDirectory();
+        return preg_match ('/^\//', Base::getDbDirectory ()) || // Linux /
+               preg_match ('/^\w\:/', Base::getDbDirectory ()); // Windows X:
+    }
+
     public static function noDatabaseSelected () {
         return self::isMultipleDatabaseEnabled () && is_null (GetUrlParam (DB));
     }
diff --git a/data.php b/data.php
index 33c5343..606dd5c 100644
--- a/data.php
+++ b/data.php
@@ -150,8 +150,7 @@ class Data extends Base {
 
         $urlParam = addURLParameter("", "data", $idData);
 
-        if (preg_match ('/^\//', Base::getDbDirectory ()) || // Linux /
-            preg_match ('/^\w\:/', Base::getDbDirectory ()) || // Windows X:
+        if (Base::useAbsolutePath () ||
             $rel == Link::OPDS_THUMBNAIL_TYPE ||
             ($type == "epub" && $config['cops_update_epub-metadata']))
         {