diff --git a/sys/amd64/include/param.h b/sys/amd64/include/param.h
index 6a86a624147..293f909eb15 100644
--- a/sys/amd64/include/param.h
+++ b/sys/amd64/include/param.h
@@ -117,7 +117,9 @@
 
 #define IOPAGES	2		/* pages of i/o permission bitmap */
 
+#ifndef	KSTACK_PAGES
 #define	KSTACK_PAGES	4	/* pages of kstack (with pcb) */
+#endif
 #define	KSTACK_GUARD_PAGES 1	/* pages of kstack guard; 0 disables */
 #define UAREA_PAGES	1	/* holds struct user WITHOUT PCB (see def.) */