diff --git a/micropython/extmod/modtrezormsg/unix-usb-mock.h b/micropython/extmod/modtrezormsg/unix-usb-mock.h
index 6ee160a5..6fd8dbe4 100644
--- a/micropython/extmod/modtrezormsg/unix-usb-mock.h
+++ b/micropython/extmod/modtrezormsg/unix-usb-mock.h
@@ -26,3 +26,6 @@ int usb_vcp_add(const usb_vcp_info_t *info) {
 
 void pendsv_kbd_intr(void) {
 }
+
+void mp_hal_set_vcp_iface(int iface_num) {
+}