Escape table name of attached database in SQLite?

According to this answer, you can escape a table name by putting double-quotes around it. The SQLite documentation further states that brackets and back-ticks are also possible for compatibility with other systems.

This works on tables from the current database, however, when I try to do this on an attached database I get an error:

ATTACH db2 AS x; SELECT * FROM "x.table1"

yields the error:

no such table: x.table1

If I remove the "x." and run the query directly on database db2, it works.

So how do I escape the table name when it is part of an attached database?

I have tried the brackets and backticks, and I have also tried quoting only the table name and not the "x." part.