diff --git a/src/emu/diserial.c b/src/emu/diserial.c
index e830e1056b1..f74700bfcb7 100644
--- a/src/emu/diserial.c
+++ b/src/emu/diserial.c
@@ -42,6 +42,7 @@ device_serial_interface::device_serial_interface(const machine_config &mconfig,
 	m_tra_baud = 0;
 	m_rcv_baud = 0;
 	m_tra_flags = 0;
+	m_rcv_register_data = 0x8000;
 }
 
 device_serial_interface::~device_serial_interface()