diff --git a/drivers/serial/serial_s3c24x0.c b/drivers/serial/serial_s3c24x0.c
index 3a703b6..abc08e0 100644
--- a/drivers/serial/serial_s3c24x0.c
+++ b/drivers/serial/serial_s3c24x0.c
@@ -72,6 +72,8 @@
 	writew(0x0245, base + UCON);
 
 #ifdef CONFIG_DRIVER_SERIAL_S3C24X0_AUTOSYNC
+	writeb(0x10, base + UMCON); /* enable auto flow control */
+#else
 	writeb(0x01, base + UMCON); /* RTS up */
 #endif