With a new experimental library for running Jepsen tests on Amazon RDS clusters, we report on a small issue in Amazon RDS for PostgreSQL. At the “Repeatable Read” isolation level, which in PostgreSQL normally means Snapshot Isolation, Amazon RDS for PostgreSQL clusters appear to exhibit Long Fork. We observed this behavior in healthy clusters, in versions ranging from 13.15 to 17.4. Amazon RDS for PostgreSQL may instead support Parallel Snapshot Isolation, a slightly weaker consistency model.