diff --git a/drivers/serial/serial_s3c24x0.c b/drivers/serial/serial_s3c24x0.c
index fedddd3..d7eac8f 100644
--- a/drivers/serial/serial_s3c24x0.c
+++ b/drivers/serial/serial_s3c24x0.c
@@ -113,7 +113,7 @@
 {
 	struct device_d *dev = cdev->dev;
 
-	while (!readb(dev->map_base + UTRSTAT) & 0x4)
+	while (!(readb(dev->map_base + UTRSTAT) & 0x4))
 		;
 }