diff --git a/src/devices/machine/i8251.c b/src/devices/machine/i8251.c
index 0f116ae0961..6e45d13a1ea 100644
--- a/src/devices/machine/i8251.c
+++ b/src/devices/machine/i8251.c
@@ -658,6 +658,7 @@ WRITE8_MEMBER(i8251_device::data_w)
 
 	/* writing clears */
 	m_status &=~I8251_STATUS_TX_READY;
+	update_tx_ready();
 
         // Store state of tx enable when writing to DB buffer
         if (is_tx_enabled()) {