diff --git a/usr.sbin/acpi/acpidump/acpidump.h b/usr.sbin/acpi/acpidump/acpidump.h
index 0b7712aea27..231f49358e2 100644
--- a/usr.sbin/acpi/acpidump/acpidump.h
+++ b/usr.sbin/acpi/acpidump/acpidump.h
@@ -302,7 +302,7 @@ struct MCFGbody {
 		uint8_t		start;		/* Starting bus number */
 		uint8_t		end;		/* Ending bus number */
 		uint8_t		rsvd[4];	/* Reserved */
-	} s[];
+	} s[1] __packed;
 } __packed;
 
 /*