mysql-test variables fails on 5.0.77 with --with-debug

When compiled with --with-debug, mysql-test fails:
variables [ fail ]

mysqltest: At line 245: query 'set long_query_time=100' failed: 2013: Lost connection to MySQL server during query

The result from queries just before the failure was:
< snip >
select @@delay_key_write;
@@delay_key_write
ALL
set global delay_key_write=1;
select @@delay_key_write;
@@delay_key_write
ON
set global delayed_insert_limit=100;
set global delayed_insert_timeout=100;
set global delayed_queue_size=100;
set global flush=1;
set global flush_time=100;
set insert_id=1;
set interactive_timeout=100;
set join_buffer_size=100;
Warnings:
Warning 1292 Truncated incorrect join_buffer_size value: '100'
set last_insert_id=1;
set global local_infile=1;
set long_query_time=100;

A quote from .err log:

CURRENT_TEST: variables
090602 9:05:52 [Warning] option 'net_buffer_length': unsigned value 1 adjusted to 1024
090602 9:05:52 [Warning] option 'binlog_cache_size': unsigned value 100 adjusted to 4096
090602 9:05:52 [Warning] option 'join_buffer_size': unsigned value 100 adjusted to 8200
mysqld: my_getopt.c:830: getopt_ull_limit_value: Assertion `(optp->var_type & 127) == 8' failed.
090602 9:05:52 - mysqld got signal 6 ;