diff --git a/lisp/org.el b/lisp/org.el
index f4fd40201..5028c43d5 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -75,6 +75,7 @@
   (require 'gnus-sum))
 
 (require 'calendar)
+(require 'format-spec)
 
 ;; Emacs 22 calendar compatibility:  Make sure the new variables are available
 (when (fboundp 'defvaralias)