Here's a patch. It was just a matter of calling a different function.
Index: modules/mappers/mod_negotiation.c =================================================================== --- modules/mappers/mod_negotiation.c.orig +++ modules/mappers/mod_negotiation.c @@ -2791,7 +2791,7 @@ static int setup_choice_response(request } apr_table_setn(r->err_headers_out, "Content-Location", - ap_escape_path_segment(r->pool, variant->file_name)); + ap_os_escape_path(r->pool, variant->file_name, 0)); set_neg_headers(r, neg, alg_choice); /* add Alternates and Vary */