SQL error occurred when upgrading database from 2.0.x to 2.1.x:

11847:20130801:113511.539 query [txnlev:1] [begin;]
11847:20130801:113511.539 query [txnlev:1] [alter table httptest change column macros variables text default '' not null]
11847:20130801:113511.539 [Z3005] query failed: [1101] BLOB/TEXT column 'variables' can't have a default value [alter table httptest change column macros variables text default '' not null]
11847:20130801:113511.539 query [alter table httptest change column macros variables text default '' not null] failed, setting transaction as failed
11847:20130801:113511.540 query [txnlev:1] [rollback;]
11847:20130801:113511.540 database upgrade failed
11847:20130801:113511.540 End of DBcheck_version():FAIL