Semijoin inflates number of rows in query result

Turning semijoin optimization on/off can affect number of rows returned by a query.

Enabling semojoin optimisation can cause a query like that:

SELECT * FROM manufacturers WHERE (...);

to return more rows than:

SELECT * FROM manufacturers;

Please, find a full test case setup attached.

Just to sum up the test case:
It executes the query below: (manufacturers table size: 2)

SELECT * FROM manufacturers WHERE manufacturers.id IN (             

  SELECT ships.manufacturers_id FROM owners JOIN ships ON owners.id = ships.owners_id WHERE owners.id = 1

);

Then the query returns:

• 2 rows ( SET optimizer_switch='semijoin=off'; )
• 3 rows ( SET optimizer_switch='semijoin=on'; )