We need to use non automatic generated ids in our database. Value for primary key is generated manually before saving newly created AR object. Creating new record in database invokes ::JdbcSpec::PostgreSQL.insert method. It tries to get value for primary key from sequence, regardless of the fact that it was already specified. As a workaround we use monkey patch: ::JdbcSpec::PostgreSQL.module_eval do def insert_with_id(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil) if id_value execute(sql, name) return id_value else insert_without_id(sql, name, pk, id_value, sequence_name) end end alias_method_chain :insert, :id end