diff --git a/lisp/babel/ob.el b/lisp/babel/ob.el
index c6aa7d24a..7da15f7ed 100644
--- a/lisp/babel/ob.el
+++ b/lisp/babel/ob.el
@@ -30,6 +30,7 @@
 
 ;;; Code:
 (eval-when-compile (require 'cl))
+(require 'outline)
 
 (defvar org-babel-call-process-region-original)
 (declare-function show-all "outline" ())