Generating a futureRollbackSql when using "classpath:" prefix doesn't recognise any of the ran change sets.

I was running some code that generated an updateSql and a rollbackSql at the same time. They both lined up and all was fine. However after applying the updateSql I regenerated the rollbackSql to find that the rollbackSql was still the same as before.
It worked fine when I has a changelog without the classpath: prefix.