Created attachment 15199 [details] rsync_allow_old_max_block_size_in_options.patch Old large block sizes with protocol < 30 aren't allowed due to a check in options.c added in commit: d74512eb054666198203cdaaaca29a18ba958725. I have attached a patch which fixes this problem.
Thanks for the patch. I've put something similar into options.c to fix this.