diff -ruN putty-0.60.orig/unix/uxmisc.c putty-0.60/unix/uxmisc.c
--- putty-0.60.orig/unix/uxmisc.c	2007-01-20 21:13:57.000000000 +0700
+++ putty-0.60/unix/uxmisc.c	2010-07-22 21:28:42.000000000 +0800
@@ -141,7 +141,7 @@
 	return fopen(filename.path, mode);
     } else {
 	int fd;
-	assert(mode[0] == 'w');	       /* is_private is meaningless for read */
+	assert(mode[0] == 'w' || mode[0] == 'a');	       /* is_private is meaningless for read */
 	fd = open(filename.path, O_WRONLY | O_CREAT | O_TRUNC,
 		      0700);
 	if (fd < 0)