diff --git a/lib/file_api.php b/lib/file_api.php
--- a/lib/file_api.php
+++ b/lib/file_api.php
@@ -370,7 +370,7 @@
      */
     public function file_url($file)
     {
-        return $this->api_url() . '?method=file_get'
+        return $this->api_url() . '/?method=file_get'
             . '&file=' . urlencode($file)
             . '&token=' . urlencode(session_id());
     }