diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -2667,6 +2667,8 @@
     sysctl_vm_object_list_swap, "S,kinfo_vmobject",
     "List of swap VM objects");
 
+SYSCTL_SIZEOF_STRUCT(vm_object);
+
 #include "opt_ddb.h"
 #ifdef DDB
 #include <sys/kernel.h>