diff --git a/networking/ftpgetput.c b/networking/ftpgetput.c
index fa18549..3773f99 100644
--- a/networking/ftpgetput.c
+++ b/networking/ftpgetput.c
@@ -124,7 +124,8 @@
 	fd_data = xconnect_ftpdata(server, buf);
 
 	if (ftpcmd("SIZE ", server_path, control_stream, buf) == 213) {
-		if (SAFE_STRTOOFF(buf + 4, &filesize))
+		filesize = BB_STRTOOFF(buf + 4, NULL, 10);
+		if (errno || filesize < 0)
 			bb_error_msg_and_die("SIZE error: %s", buf + 4);
 	} else {
 		filesize = -1;