diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
--- a/sys/kern/subr_kdb.c
+++ b/sys/kern/subr_kdb.c
@@ -238,7 +238,7 @@
 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
 {
 	int error, i;
-	int *addr = (int *)0x10;
+	int *volatile addr = (int *)0x10;
 
 	error = sysctl_wire_old_buffer(req, sizeof(int));
 	if (error == 0) {