--- src/optipng.c_orig	2007-09-09 10:02:38.000000000 +0200
+++ src/optipng.c	2007-09-09 10:03:56.000000000 +0200
@@ -298,6 +298,8 @@
       vfprintf(confile, fmt, arg_ptr);
    if (global.logfile != NULL)
    {
+      va_end(arg_ptr);
+      va_start(arg_ptr, fmt);
       vfprintf(global.logfile, fmt, arg_ptr);
       fflush(global.logfile);
    }