diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 810a1b0b65203..10e9f983de621 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -807,13 +807,22 @@ static void stm32_usart_set_termios(struct uart_port *port,
 	 * CS8 or (CS7 + parity), 8 bits word aka [M1:M0] = 0b00
 	 * M0 and M1 already cleared by cr1 initialization.
 	 */
-	if (bits == 9)
+	if (bits == 9) {
 		cr1 |= USART_CR1_M0;
-	else if ((bits == 7) && cfg->has_7bits_data)
+	} else if ((bits == 7) && cfg->has_7bits_data) {
 		cr1 |= USART_CR1_M1;
-	else if (bits != 8)
+	} else if (bits != 8) {
 		dev_dbg(port->dev, "Unsupported data bits config: %u bits\n"
 			, bits);
+		cflag &= ~CSIZE;
+		cflag |= CS8;
+		termios->c_cflag = cflag;
+		bits = 8;
+		if (cflag & PARENB) {
+			bits++;
+			cr1 |= USART_CR1_M0;
+		}
+	}
 
 	if (ofs->rtor != UNDEF_REG && (stm32_port->rx_ch ||
 				       (stm32_port->fifoen &&