diff --git a/sys/ia64/ia64/genassym.c b/sys/ia64/ia64/genassym.c
index 02563548869f..808758b0eb37 100644
--- a/sys/ia64/ia64/genassym.c
+++ b/sys/ia64/ia64/genassym.c
@@ -37,6 +37,8 @@
  * $FreeBSD$
  */
 
+#include "opt_kstack_pages.h"
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/assym.h>