Originally:

https://github.com/mjg59/pupnp-code/commit/be0a01bdb83395d9f3a5ea09c1308a4f1a972cbd

But without the configure bits, because we're just going to leave it disabled
anyway, and I don't feel like making autoreconf work.

diff -up libupnp-1.6.20/upnp/src/genlib/net/http/webserver.c.jx libupnp-1.6.20/upnp/src/genlib/net/http/webserver.c
--- libupnp-1.6.20/upnp/src/genlib/net/http/webserver.c.jx	2016-07-07 13:05:30.000000000 -0400
+++ libupnp-1.6.20/upnp/src/genlib/net/http/webserver.c	2016-07-18 14:02:23.920747068 -0400
@@ -1367,9 +1367,13 @@ static int http_RecvPostMessage(
 		if (Fp == NULL)
 			return HTTP_INTERNAL_SERVER_ERROR;
 	} else {
+#ifdef UPNP_ENABLE_POST_WRITE
 		Fp = fopen(filename, "wb");
 		if (Fp == NULL)
 			return HTTP_UNAUTHORIZED;
+#else
+		return HTTP_NOT_FOUND;
+#endif
 	}
 	parser->position = POS_ENTITY;
 	do {