Where expression with NOT function gives incorrect result

mysql> create table t1(c1 int);

Query OK, 0 rows affected (0.01 sec)

mysql> insert into t1 values(1);

elect *Query OK, 1 row affected (0.00 sec)

mysql> select * from t1 where ( (c1 is not null) >= (not true) ) is not null;

Empty set (0.00 sec)

mysql> select version();

+---------------------+

| version()           |

+---------------------+

| 10.1.10-MariaDB-log |

+---------------------+

1 row in set (0.00 sec)

drop table t1;

create table t1(c1 int);

insert into t1 values(1);

select * from t1 where ( (c1 is not null) >= (not true) ) is not null;