diff --git a/drivers/char/mxser.h b/drivers/char/mxser.h
index 9fe28497eae9ed51b8780673cd111456b1ff8aec..1f4aa45ec004436aac1e80b03eb46dac02876741 100644
--- a/drivers/char/mxser.h
+++ b/drivers/char/mxser.h
@@ -30,8 +30,7 @@
 
 #define TTY_THRESHOLD_THROTTLE  128
 
-#define LO_WATER	 	(TTY_FLIPBUF_SIZE)
-#define HI_WATER		(TTY_FLIPBUF_SIZE*2*3/4)
+#define HI_WATER		768
 
 // added by James. 03-11-2004.
 #define MOXA_SDS_GETICOUNTER  	(MOXA + 68)