diff --git a/libraries/wutdevoptab/devoptab_fs_open.c b/libraries/wutdevoptab/devoptab_fs_open.c
index 811ee365..7a60fbe4 100644
--- a/libraries/wutdevoptab/devoptab_fs_open.c
+++ b/libraries/wutdevoptab/devoptab_fs_open.c
@@ -59,6 +59,7 @@ __wut_fs_open(struct _reent *r,
    file = (__wut_fs_file_t *)fileStruct;
    file->fd = fd;
    file->flags = (flags & (O_ACCMODE|O_APPEND|O_SYNC));
+   file->offset = 0;
    if (flags & O_APPEND) {
       status = FSGetPosFile(__wut_devoptab_fs_client, &cmd, fd, &file->offset, FS_ERROR_FLAG_ALL);
       if (status < 0) {
diff --git a/libraries/wutdevoptab/devoptab_fs_read.c b/libraries/wutdevoptab/devoptab_fs_read.c
index a10ccbb9..1f66a657 100644
--- a/libraries/wutdevoptab/devoptab_fs_read.c
+++ b/libraries/wutdevoptab/devoptab_fs_read.c
@@ -56,6 +56,7 @@ ssize_t __wut_fs_read(struct _reent *r, void *fd, char *ptr, size_t len) {
          memcpy(ptr, alignedBuffer, status);
       }
 
+      file->offset += status;
       bytesRead += status;
       ptr += status;
 
diff --git a/libraries/wutdevoptab/devoptab_fs_write.c b/libraries/wutdevoptab/devoptab_fs_write.c
index 377bbe10..5259c272 100644
--- a/libraries/wutdevoptab/devoptab_fs_write.c
+++ b/libraries/wutdevoptab/devoptab_fs_write.c
@@ -53,6 +53,7 @@ ssize_t __wut_fs_write(struct _reent *r, void *fd, const char *ptr, size_t len)
          return -1;
       }
 
+      file->offset += status;
       bytesWritten += status;
       ptr += status;