diff --git a/lisp/simple.el b/lisp/simple.el
index aa0724e87d8f4acd088200ddb2cfd2d71ffe3a36..95b519cf5ca81812b17faad720d5dc7016d7a637 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -105,6 +105,8 @@ If `fringe-arrow', indicate the locus by the fringe arrow."
   :group 'next-error
   :version "22.1")
 
+(defvar next-error-highlight-timer nil)
+
 (defvar next-error-last-buffer nil
   "The most recent next-error buffer.
 A buffer becomes most recent when its compilation, grep, or