diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index 63a9ef6..fe6cc26 100644
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -253,7 +253,7 @@
 {
 	struct NS16550 *const com_port = dev_get_priv(dev);
 
-	if (!serial_in(&com_port->lsr) & UART_LSR_DR)
+	if (!(serial_in(&com_port->lsr) & UART_LSR_DR))
 		return -EAGAIN;
 
 	return serial_in(&com_port->rbr);