diff --git a/hw/riscv/opentitan.c b/hw/riscv/opentitan.c
index 9535308197..6a2fcc4ade 100644
--- a/hw/riscv/opentitan.c
+++ b/hw/riscv/opentitan.c
@@ -78,8 +78,8 @@ static const MemMapEntry ibex_memmap[] = {
 static void opentitan_machine_init(MachineState *machine)
 {
     MachineClass *mc = MACHINE_GET_CLASS(machine);
+    OpenTitanState *s = OPENTITAN_MACHINE(machine);
     const MemMapEntry *memmap = ibex_memmap;
-    OpenTitanState *s = g_new0(OpenTitanState, 1);
     MemoryRegion *sys_mem = get_system_memory();
 
     if (machine->ram_size != mc->default_ram_size) {
@@ -330,6 +330,7 @@ static const TypeInfo open_titan_types[] = {
     }, {
         .name           = TYPE_OPENTITAN_MACHINE,
         .parent         = TYPE_MACHINE,
+        .instance_size  = sizeof(OpenTitanState),
         .class_init     = opentitan_machine_class_init,
     }
 };
diff --git a/include/hw/riscv/opentitan.h b/include/hw/riscv/opentitan.h
index 806ff73528..609473d07b 100644
--- a/include/hw/riscv/opentitan.h
+++ b/include/hw/riscv/opentitan.h
@@ -55,10 +55,11 @@ struct LowRISCIbexSoCState {
 };
 
 #define TYPE_OPENTITAN_MACHINE MACHINE_TYPE_NAME("opentitan")
+OBJECT_DECLARE_SIMPLE_TYPE(OpenTitanState, OPENTITAN_MACHINE)
 
 typedef struct OpenTitanState {
     /*< private >*/
-    SysBusDevice parent_obj;
+    MachineState parent_obj;
 
     /*< public >*/
     LowRISCIbexSoCState soc;