DROP SCHEMA fails

[myzlab]

I am trying to parse the following query:

DROP SCHEMA ex;

and I receive the next error:

Syntax error at line 1 col 13:

1 DROP SCHEMA ex;
Unexpected word token: "ex".
I did not expect any more input. Here is the state of my parse table:

kw_index → %word
kw_trigger → %word
kw_type → %word
kw_sequence → %word
kw_function → %word