I am using FB WI-T1.0.0.679 .

1. I make field DST_MAG of table MV_LI NOT NULL with the following command

update RDB$RELATION_FIELDS set
RDB$NULL_FLAG = 1
where (RDB$FIELD_NAME = 'DST_MAG') and
(RDB$RELATION_NAME = 'MV_LI')

and commit

2. I issue the command

update MV_LI set DST_MAG=NULL

and correctly get the error message

"validation error for column DST_MAG, value ***null***"

3. I make field DST_MAG of table MV_LI nullable with the following command

update RDB$RELATION_FIELDS set
RDB$NULL_FLAG = 0
where (RDB$FIELD_NAME = 'DST_MAG') and
(RDB$RELATION_NAME = 'MV_LI')

and commit

4. I repeat step 2. AND GET THE SAME ERROR MESSAGE

5. in order to store the NULL value into field DST_MAG, I have to drop the
field and add it again

Isn't this a bug ?

Thank you

Duilio Foschi