mksession saves closed buffers when it should not

Here is my sessionoptions:
sessionoptions=blank,curdir,folds,help,options,tabpages,winsize
(removed the 'buffer' defaults)

I open 3 tabs with 'vim -p *py'.
I close one of those tabs and save session with 'mksession!'.
When I 'vim -S session.vim' it still open 3 tabs including the closed one.

I have also tried to 'bdelete' this buffer and have read the 'mksession' and 'sessionoptions' help with no success.

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.