DROP TABLE IF EXISTS issue. Exception: no such table: tablename (SQLite3::Exception)

[vectorselector]

DB.open "sqlite3:./mydb.sqlite3" do |db|
db.exec "DROP TABLE IF EXISTS tablename"
end

triggers "Exception: no such table: tablename (SQLite3::Exception)"

when:

sqlite3 mydb.sqlite3
SQLite version 3.31.1 2020-01-27 19:55:54
Enter ".help" for usage hints.
sqlite> .tables
tablename

1. table exists
2. sqlite3 implements "DROP TABLE IF EXISTS tablename" which should NOT trigger any exception.
3. crystal-sqlite3 test spec https://github.com/crystal-lang/crystal-sqlite3/blob/master/spec/db_spec.cr
   specifically invokes (lines 81-83)

drop_table_if_exists_syntax do |table_name|
"drop table if exists #{table_name}"
end

4. I cleaned cache ~/.cache/crystal/

crystal version 1.7.3

What am I doing wrong?