diff --git a/include/tty.h b/include/tty.h
index 0aebf9d790..8afe9101f2 100644
--- a/include/tty.h
+++ b/include/tty.h
@@ -37,21 +37,19 @@ struct tty_serial {
  * "tty" device provides support for buffered, interrupt-driven,
  * timeout-controlled access to an underlying UART device. For
  * completeness, it also support non-interrupt-driven, busy-polling
- * access mode.
+ * access mode. After initialization, tty is in the "most conservative"
+ * unbuffered mode with infinite timeouts (this is guaranteed to work
+ * on any hardware). Users should configure buffers and timeouts as
+ * they need using functions tty_set_rx_buf(), tty_set_tx_buf(),
+ * tty_set_rx_timeout(), tty_set_tx_timeout().
  *
  * @param tty tty device structure to initialize
  * @param uart_dev underlying UART device to use (should support
  *                 interrupt-driven operation)
- * @param rxbuf pointer to receive buffer
- * @param rxbuf_sz size of receive buffer
- * @param txbuf pointer to transmit buffer
- * @param txbuf_sz size of transmit buffer
  *
- * @return N/A
+ * @return 0 on success, error code (<0) otherwise
  */
-void tty_init(struct tty_serial *tty, struct device *uart_dev,
-	      u8_t *rxbuf, u16_t rxbuf_sz,
-	      u8_t *txbuf, u16_t txbuf_sz);
+int tty_init(struct tty_serial *tty, struct device *uart_dev);
 
 /**
  * @brief Set receive timeout for tty device.
diff --git a/subsys/console/getchar.c b/subsys/console/getchar.c
index 0700ba332f..dfc771bf28 100644
--- a/subsys/console/getchar.c
+++ b/subsys/console/getchar.c
@@ -51,7 +51,7 @@ void console_init(void)
 	struct device *uart_dev;
 
 	uart_dev = device_get_binding(CONFIG_UART_CONSOLE_ON_DEV_NAME);
-	tty_init(&console_serial, uart_dev,
-		 console_rxbuf, sizeof(console_rxbuf),
-		 console_txbuf, sizeof(console_txbuf));
+	tty_init(&console_serial, uart_dev);
+	tty_set_tx_buf(&console_serial, console_txbuf, sizeof(console_txbuf));
+	tty_set_rx_buf(&console_serial, console_rxbuf, sizeof(console_rxbuf));
 }
diff --git a/subsys/console/tty.c b/subsys/console/tty.c
index 39e9f28bd2..41830c75fe 100644
--- a/subsys/console/tty.c
+++ b/subsys/console/tty.c
@@ -238,24 +238,24 @@ ssize_t tty_read(struct tty_serial *tty, void *buf, size_t size)
 	return out_size;
 }
 
-void tty_init(struct tty_serial *tty, struct device *uart_dev,
-	      u8_t *rxbuf, u16_t rxbuf_sz,
-	      u8_t *txbuf, u16_t txbuf_sz)
+int tty_init(struct tty_serial *tty, struct device *uart_dev)
 {
 	tty->uart_dev = uart_dev;
-	tty->rx_ringbuf = rxbuf;
-	tty->rx_ringbuf_sz = rxbuf_sz;
-	tty->tx_ringbuf = txbuf;
-	tty->tx_ringbuf_sz = txbuf_sz;
+
+	/* We start in unbuffer mode. */
+	tty->rx_ringbuf = NULL;
+	tty->rx_ringbuf_sz = 0;
+	tty->tx_ringbuf = NULL;
+	tty->tx_ringbuf_sz = 0;
+
 	tty->rx_get = tty->rx_put = tty->tx_get = tty->tx_put = 0;
-	k_sem_init(&tty->rx_sem, 0, UINT_MAX);
-	k_sem_init(&tty->tx_sem, txbuf_sz - 1, UINT_MAX);
 
 	tty->rx_timeout = K_FOREVER;
 	tty->tx_timeout = K_FOREVER;
 
 	uart_irq_callback_user_data_set(uart_dev, tty_uart_isr, tty);
-	uart_irq_rx_enable(uart_dev);
+
+	return 0;
 }
 
 int tty_set_rx_buf(struct tty_serial *tty, void *buf, size_t size)
@@ -266,6 +266,7 @@ int tty_set_rx_buf(struct tty_serial *tty, void *buf, size_t size)
 	tty->rx_ringbuf_sz = size;
 
 	if (size > 0) {
+		k_sem_init(&tty->rx_sem, 0, UINT_MAX);
 		uart_irq_rx_enable(tty->uart_dev);
 	}
 
@@ -279,6 +280,8 @@ int tty_set_tx_buf(struct tty_serial *tty, void *buf, size_t size)
 	tty->tx_ringbuf = buf;
 	tty->tx_ringbuf_sz = size;
 
+	k_sem_init(&tty->tx_sem, size - 1, UINT_MAX);
+
 	/* New buffer is initially empty, no need to re-enable interrupts,
 	 * it will be done when needed (on first output char).
 	 */