Index: sys/kern/init_main.c
===================================================================
--- sys/kern/init_main.c
+++ sys/kern/init_main.c
@@ -117,6 +117,12 @@
 SYSCTL_INT(_debug, OID_AUTO, bootverbose, CTLFLAG_RW, &bootverbose, 0,
 	"Control the output of verbose kernel messages");
 
+#ifdef INVARIANTS
+static int	invariants = 1;
+SYSCTL_INT(_debug, OID_AUTO, invariants, CTLFLAG_RO, &invariants, 0,
+	"Kernel compiled with invariants");
+#endif
+
 /*
  * This ensures that there is at least one entry so that the sysinit_set
  * symbol is not undefined.  A sybsystem ID of SI_SUB_DUMMY is never