FlinkStatistic does not compile on later Scala versions

After upgrading Scala to 2.12.15 for testing purposes (because 2.12.7 does not work on Java 17), I got a compile error int he FlinkStatistic.

[ERROR] FlinkStatistic.scala:146: error: Int does not take parameters
[ERROR]     if (builder.nonEmpty && builder.length() > 2) {