Unexpected "No database selected" error for a CALL inside an anonymous block

I start a command line client as just "mariadb", i.e. without the current database.
Then I run this script:

CREATE DATABASE test1;

DELIMITER $$

CREATE OR REPLACE PROCEDURE test1.p1()

BEGIN

  SELECT 1;

END;

$$

DELIMITER ;

CALL test1.p1();

+---+

| 1 |

+---+

| 1 |

+---+

It works as expected.

Now I call the procedure inside an anonymous block:

DELIMITER $$

BEGIN NOT ATOMIC

  CALL test1.p1();

END;

$$

DELIMITER ;

It return an unexpected error:

ERROR 1046 (3D000): No database selected

The failure is possibly related to MDEV-34391, as it does repease before 12.3.