diff -Naur linux-2.4.25-orig/drivers/char/serial.c linux-2.4.25/drivers/char/serial.c
--- linux-2.4.25-orig/drivers/char/serial.c	2004-02-18 05:36:31.000000000 -0800
+++ linux-2.4.25/drivers/char/serial.c	2004-03-26 18:36:25.000000000 -0800
@@ -924,7 +924,7 @@
 			transmit_chars(info, 0);
 #endif
 		if (pass_counter++ > RS_ISR_PASS_LIMIT) {
-#if SERIAL_DEBUG_INTR
+#ifdef SERIAL_DEBUG_INTR
 			printk("rs_single loop break.\n");
 #endif
 			break;