Redshift table not showing up in tables for schema?

On Redshift, why doesn't my table show up in the following query? It definitely exists, as shown by the next query I run. I want a way to list all tables for a schema:

mydb=# select distinct(tablename) from pg_table_def where schemaname = 'db';
 tablename 
-----------
(0 rows)

mydb=# \d db.some_table
                    Table "db.some_table"
     Column      |            Type             | Modifiers 
-----------------+-----------------------------+-----------
...correct info shows up here...
...but nothing showed up above?