diff --git a/core/cfs/cfs-eeprom.c b/core/cfs/cfs-eeprom.c
index 54f5cf4af..cafe674f4 100644
--- a/core/cfs/cfs-eeprom.c
+++ b/core/cfs/cfs-eeprom.c
@@ -30,7 +30,7 @@
  *
  * Author: Adam Dunkels <adam@sics.se>
  *
- * $Id: cfs-eeprom.c,v 1.6 2008/01/09 08:12:52 adamdunkels Exp $
+ * $Id: cfs-eeprom.c,v 1.7 2008/01/24 13:08:35 adamdunkels Exp $
  */
 
 #include "cfs/cfs.h"
@@ -94,7 +94,7 @@ cfs_read(int f, void *buf, unsigned int len)
 }
 /*---------------------------------------------------------------------------*/
 int
-cfs_write(int f, void *buf, unsigned int len)
+cfs_write(int f, const void *buf, unsigned int len)
 {
   if(f == 1) {
     eeprom_write(CFS_EEPROM_OFFSET + file.fileptr, buf, len);
diff --git a/core/cfs/cfs-posix.c b/core/cfs/cfs-posix.c
index bd4310ae0..21d7cb34d 100644
--- a/core/cfs/cfs-posix.c
+++ b/core/cfs/cfs-posix.c
@@ -30,7 +30,7 @@
  *
  * Author: Adam Dunkels <adam@sics.se>
  *
- * $Id: cfs-posix.c,v 1.9 2008/01/08 14:27:06 adamdunkels Exp $
+ * $Id: cfs-posix.c,v 1.10 2008/01/24 13:08:35 adamdunkels Exp $
  */
 
 #include <stdio.h>
@@ -75,7 +75,7 @@ cfs_read(int f, void *b, unsigned int l)
 }
 /*---------------------------------------------------------------------------*/
 int
-cfs_write(int f, void *b, unsigned int l)
+cfs_write(int f, const void *b, unsigned int l)
 {
   return write(f, b, l);
 }
diff --git a/core/cfs/cfs-ram.c b/core/cfs/cfs-ram.c
index 50a614cb6..c06df5c8d 100644
--- a/core/cfs/cfs-ram.c
+++ b/core/cfs/cfs-ram.c
@@ -30,7 +30,7 @@
  *
  * Author: Adam Dunkels <adam@sics.se>
  *
- * $Id: cfs-ram.c,v 1.6 2008/01/08 14:27:06 adamdunkels Exp $
+ * $Id: cfs-ram.c,v 1.7 2008/01/24 13:08:35 adamdunkels Exp $
  */
 
 #include <string.h>
@@ -106,7 +106,7 @@ cfs_read(int f, void *buf, unsigned int len)
 }
 /*---------------------------------------------------------------------------*/
 int
-cfs_write(int f, void *buf, unsigned int len)
+cfs_write(int f, const void *buf, unsigned int len)
 {
   printf("write file.fileptr %d len %d filesize %d\n",
 	 file.fileptr, len, file.filesize);
diff --git a/core/cfs/cfs-xmem.c b/core/cfs/cfs-xmem.c
index 9d4acb3bf..4dae6202e 100644
--- a/core/cfs/cfs-xmem.c
+++ b/core/cfs/cfs-xmem.c
@@ -30,7 +30,7 @@
  *
  * Author: Adam Dunkels <adam@sics.se>
  *
- * $Id: cfs-xmem.c,v 1.7 2008/01/08 14:27:06 adamdunkels Exp $
+ * $Id: cfs-xmem.c,v 1.8 2008/01/24 13:08:35 adamdunkels Exp $
  */
 
 #include "cfs/cfs.h"
@@ -110,7 +110,7 @@ cfs_read(int f, void *buf, unsigned int len)
 }
 /*---------------------------------------------------------------------------*/
 int
-cfs_write(int f, void *buf, unsigned int len)
+cfs_write(int f, const void *buf, unsigned int len)
 {
   if(file.fileptr >= CFS_XMEM_SIZE) {
     return 0;
diff --git a/core/cfs/cfs.h b/core/cfs/cfs.h
index f852785c6..85b21e1ea 100644
--- a/core/cfs/cfs.h
+++ b/core/cfs/cfs.h
@@ -54,7 +54,7 @@
  *
  * Author: Adam Dunkels <adam@sics.se>
  *
- * $Id: cfs.h,v 1.10 2008/01/08 14:27:06 adamdunkels Exp $
+ * $Id: cfs.h,v 1.11 2008/01/24 13:08:35 adamdunkels Exp $
  */
 #ifndef __CFS_H__
 #define __CFS_H__
@@ -172,7 +172,7 @@ CCIF int cfs_read(int fd, void *buf, unsigned int len);
  *             cfs_open() and the CFS_WRITE flag.
  */
 #ifndef cfs_write
-CCIF int cfs_write(int fd, void *buf, unsigned int len);
+CCIF int cfs_write(int fd, const void *buf, unsigned int len);
 #endif
 
 /**