Got error 126 / mysqld: Index for table 't' is corrupt (key_cache_segments variation)

SET sql_mode='';

SET GLOBAL key_cache_segments=10;

SET GLOBAL key_buffer_size=20000;

CREATE TEMPORARY TABLE t (a INT KEY) ENGINE=MyISAM;

INSERT INTO t VALUES (1),(2);

SET GLOBAL key_cache_block_size=2048;

SELECT * FROM t UNION SELECT * FROM t;

Leads to:

10.7.0-dbg>SELECT * FROM t UNION SELECT * FROM t;

ERROR 126 (HY000): Index for table 'riadb-10.7.0-linux-x86_64-dbg/data/#sql-temptable-3c7125-4-0.MYI' is corrupt; try to repair it

Bug confirmed present in:
MariaDB: 10.2.41 (dbg), 10.2.41 (opt), 10.3.32 (dbg), 10.3.32 (opt), 10.4.22 (dbg), 10.4.22 (opt), 10.5.13 (dbg), 10.5.13 (opt), 10.6.5 (dbg), 10.6.5 (opt), 10.7.0 (dbg), 10.7.0 (opt)

Bug (or feature/syntax) confirmed not present in:
MySQL: 5.5.62 (dbg), 5.5.62 (opt), 5.6.51 (dbg), 5.6.51 (opt), 5.7.35 (dbg), 5.7.35 (opt), 8.0.26 (dbg), 8.0.26 (opt)

Note also the chopped off/added path in the error message.