diff --git a/opengrok-restful.el b/opengrok-restful.el
index 5415fb9..6f44c7d 100644
--- a/opengrok-restful.el
+++ b/opengrok-restful.el
@@ -35,6 +35,7 @@
 
 (require 'json)
 (require 'request)
+(require 's)
 
 (setq opengrok-restful-source-directory "")
 (setq opengrok-restful-buffer "*opengrok-restful*")