diff -ru parrot-0.1.1/include/parrot/io.h parrot-io/include/parrot/io.h
--- parrot-0.1.1/include/parrot/io.h	2004-10-04 13:40:27.000000000 +0200
+++ parrot-io/include/parrot/io.h	2005-01-20 22:39:50.000000000 +0100
@@ -115,7 +115,7 @@
     void *self;                 /* Instance specific data       */
     const char *name;
     INTVAL flags;
-    ParrotIOLayerAPI *api;
+    const ParrotIOLayerAPI *api;
     ParrotIOLayer *up;
     ParrotIOLayer *down;
 };
diff -ru parrot-0.1.1/io/io_buf.c parrot-io/io/io_buf.c
--- parrot-0.1.1/io/io_buf.c	2004-09-22 10:48:31.000000000 +0200
+++ parrot-io/io/io_buf.c	2005-01-20 22:37:40.000000000 +0100
@@ -23,7 +23,7 @@
 #include <assert.h>
 
 /* Defined at bottom */
-extern ParrotIOLayerAPI pio_buf_layer_api;
+extern const ParrotIOLayerAPI pio_buf_layer_api;
 
 ParrotIOLayer pio_buf_layer = {
     NULL,
@@ -784,7 +784,7 @@
     return io->fpos;
 }
 
-ParrotIOLayerAPI pio_buf_layer_api = {
+const ParrotIOLayerAPI pio_buf_layer_api = {
     PIO_buf_init,
     PIO_base_new_layer,
     PIO_base_delete_layer,
diff -ru parrot-0.1.1/io/io_stdio.c parrot-io/io/io_stdio.c
--- parrot-0.1.1/io/io_stdio.c	2004-06-21 17:57:49.000000000 +0200
+++ parrot-io/io/io_stdio.c	2005-01-20 22:36:23.000000000 +0100
@@ -28,7 +28,7 @@
 extern INTVAL           PIO_stdio_getblksize(PIOHANDLE fd);
 
 /* Defined at bottom */
-extern ParrotIOLayerAPI pio_stdio_layer_api;
+extern const ParrotIOLayerAPI pio_stdio_layer_api;
 
 ParrotIOLayer pio_stdio_layer = {
     NULL,
@@ -445,7 +445,7 @@
     return(ftell((FILE*)io->fd));
 }
 
-ParrotIOLayerAPI pio_stdio_layer_api = {
+const ParrotIOLayerAPI pio_stdio_layer_api = {
     PIO_stdio_init,
     PIO_base_new_layer,
     PIO_base_delete_layer,
diff -ru parrot-0.1.1/io/io_unix.c parrot-io/io/io_unix.c
--- parrot-0.1.1/io/io_unix.c	2004-09-21 14:45:11.000000000 +0200
+++ parrot-io/io/io_unix.c	2005-01-20 22:36:56.000000000 +0100
@@ -33,7 +33,7 @@
 #ifdef PIO_OS_UNIX
 
 /* Defined at bottom */
-extern ParrotIOLayerAPI pio_unix_layer_api;
+extern const ParrotIOLayerAPI pio_unix_layer_api;
 
 ParrotIOLayer pio_unix_layer = {
     NULL,
@@ -1133,7 +1133,7 @@
 
 
 
-ParrotIOLayerAPI pio_unix_layer_api = {
+const ParrotIOLayerAPI pio_unix_layer_api = {
     PIO_unix_init,
     PIO_base_new_layer,
     PIO_base_delete_layer,
diff -ru parrot-0.1.1/io/io_utf8.c parrot-io/io/io_utf8.c
--- parrot-0.1.1/io/io_utf8.c	2004-05-24 15:47:40.000000000 +0200
+++ parrot-io/io/io_utf8.c	2005-01-20 22:37:18.000000000 +0100
@@ -27,7 +27,7 @@
 #include "io_private.h"
 
 /* Defined at bottom */
-static ParrotIOLayerAPI pio_utf8_layer_api;
+static const ParrotIOLayerAPI pio_utf8_layer_api;
 
 ParrotIOLayer pio_utf8_layer = {
     NULL,
@@ -62,7 +62,7 @@
     return PIO_write_down(interpreter, l->down, io, &n);
 }
 
-static ParrotIOLayerAPI pio_utf8_layer_api = {
+static const ParrotIOLayerAPI pio_utf8_layer_api = {
     PIO_null_init,
     PIO_base_new_layer,
     PIO_base_delete_layer,
diff -ru parrot-0.1.1/io/io_win32.c parrot-io/io/io_win32.c
--- parrot-0.1.1/io/io_win32.c	2004-06-21 17:57:49.000000000 +0200
+++ parrot-io/io/io_win32.c	2005-01-20 22:38:00.000000000 +0100
@@ -34,7 +34,7 @@
 #  include <tchar.h>
 
 /* Defined at bottom */
-extern ParrotIOLayerAPI pio_win32_layer_api;
+extern const ParrotIOLayerAPI pio_win32_layer_api;
 
 ParrotIOLayer pio_win32_layer = {
     NULL,
@@ -725,7 +725,7 @@
 /************************************************************************************************************/
 
 
-ParrotIOLayerAPI pio_win32_layer_api = {
+const ParrotIOLayerAPI pio_win32_layer_api = {
     PIO_win32_init,
     PIO_base_new_layer,
     PIO_base_delete_layer,