Error 6455 when adding column

I'm running Vertica 7.1.1-0 and I have a pretty big table that I need to add a few columns to. However, when I try to run the following query:

alter table flexgroup.tblfacturation add column FlexUtiliseVieBaseAdherent decimal(14,4);

I get the following message:

SQL Error [6455] [0A000]: [Vertica]VJDBC ROLLBACK: Unsupported access to table with projection expressions or aggregates
[Vertica]VJDBC ROLLBACK: Unsupported access to table with projection expressions or aggregates
com.vertica.util.ServerException: [Vertica]VJDBC ROLLBACK: Unsupported access to table with projection expressions or aggregates

I also tried:

alter table flexgroup.tblfacturation add column FlexUtiliseVieBaseAdherent decimal(14,4) CASCADE;

But the message this time was:

SQL Error [4856] [42601]: [Vertica]VJDBC ERROR: Syntax error at or near "CASCADE"
[Vertica]VJDBC ERROR: Syntax error at or near "CASCADE"
com.vertica.util.ServerException: [Vertica]VJDBC ERROR: Syntax error at or near "CASCADE"

After some research, I was able to figure out it has something to do with projections and the like, but I couldn't find any way to actually add the column without destroying the table and recreating it (which kind of feels like overkill).

Anyway, can anyone help me?