TokuDB: insert into select... cases table lock

I'm running 2 concurrent statements:

• Insert into tab2 select * from tab1 where ....; -- tab1 is a partitioned tokudb table
• Insert into tab1 values (...);

tab1 acquires a table lock, and the 2nd insert is waiting for "Waiting for table level lock"

Any ideas?

Thanks,

This seems to be related to this bug: https://jira.mariadb.org/browse/MDEV-9027

Thanks