@evpaassen Java 1.6 does not backfire. we have to work withing the given environment, and that is just a challenge. I'm just a bit surprised we did not see this during testing, but perhaps ci is running java 8 in java 6 compliance mode? thus not detecting the problem?
If you'd assume OpenJDK6 behaves exactly the same as Oracle JDK6. But most likely, it will not. Testing with OpenJDK6 tests compatibility with OpenJDK6, as testing with Oracle JDK6 would tell you something about compatibility with Oracle JDK6.