diff --git a/src/include/86box/machine.h b/src/include/86box/machine.h
index 1f9ed480f..af44e3744 100644
--- a/src/include/86box/machine.h
+++ b/src/include/86box/machine.h
@@ -658,6 +658,7 @@ extern int machine_at_tx97_init(const machine_t *);
 extern int machine_at_an430tx_init(const machine_t *);
 #endif
 extern int machine_at_ym430tx_init(const machine_t *);
+extern int machine_at_thunderbolt_init(const machine_t *);
 extern int machine_at_mb540n_init(const machine_t *);
 extern int machine_at_56a5_init(const machine_t *);
 extern int machine_at_p5mms98_init(const machine_t *);