Incorrect result for locking reads after INSERT of another transaction

/* init */ CREATE TABLE t(a INT PRIMARY KEY);

/* t1 */ SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;

/* t2 */ SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;

/* t1 */ BEGIN;

/* t2 */ BEGIN;

/* t1 */ INSERT INTO t(a) VALUES (2);

/* t2 */ SELECT a FROM t FOR UPDATE;  -- actual: [2], expected: [1, 2]

/* t1 */ INSERT INTO t(a) VALUES (1);

/* t1 */ COMMIT;

/* t2 */ COMMIT;