Borrowed from the curlftpfs_0.9.2-5 Debian package.

CURLOPT_INFILESIZE does not support -1 arg. This fix bug #556012.
--- curlftpfs-0.9.2/ftpfs.c.old	2009-12-13 14:12:25.000000000 +0100
+++ curlftpfs-0.9.2/ftpfs.c	2009-12-13 14:12:32.000000000 +0100
@@ -503,7 +503,6 @@
   
   curl_easy_setopt_or_die(fh->write_conn, CURLOPT_URL, fh->full_path);
   curl_easy_setopt_or_die(fh->write_conn, CURLOPT_UPLOAD, 1);
-  curl_easy_setopt_or_die(fh->write_conn, CURLOPT_INFILESIZE, -1);
   curl_easy_setopt_or_die(fh->write_conn, CURLOPT_READFUNCTION, write_data_bg);
   curl_easy_setopt_or_die(fh->write_conn, CURLOPT_READDATA, fh);
   curl_easy_setopt_or_die(fh->write_conn, CURLOPT_LOW_SPEED_LIMIT, 1);