diff -urN asterisk-1.2.18.orig/channels/chan_sip.c asterisk-1.2.18/channels/chan_sip.c
--- asterisk-1.2.18.orig/channels/chan_sip.c	2007-04-25 01:05:06.000000000 +0900
+++ asterisk-1.2.18/channels/chan_sip.c	2007-06-26 10:15:53.547559968 +0900
@@ -439,7 +439,7 @@
 
 static struct sched_context *sched;
 static struct io_context *io;
-static int *sipsock_read_id;
+static int *sipsock_read_id = NULL;
 
 #define SIP_MAX_HEADERS		64			/*!< Max amount of SIP headers to read */
 #define SIP_MAX_LINES 		64			/*!< Max amount of lines in SIP attachment (like SDP) */
@@ -11621,8 +11621,12 @@
 			sip_do_reload();
 
 			/* Change the I/O fd of our UDP socket */
-			if (sipsock > -1)
-				sipsock_read_id = ast_io_change(io, sipsock_read_id, sipsock, NULL, 0, NULL);
+			if (sipsock > -1) {
+				if (sipsock_read_id)
+					sipsock_read_id = ast_io_change(io, sipsock_read_id, sipsock, NULL, 0, NULL);
+				else
+					sipsock_read_id = ast_io_add(io, sipsock, sipsock_read, AST_IO_IN, NULL);
+			}
 		}
 		/* Check for interfaces needing to be killed */
 		ast_mutex_lock(&iflock);