#5 problem with formatting negative period

I'm trying to format negative period with formatter built with
new PeriodFormatterBuilder().appendHours().appendSeparatorIfFieldsBefore(":").printZeroAlways().minimumPrintedDigits(2).appendMinutes().toFormatter();

the problem is, if period is negative I get something like -6:-23
minus sign should be only added before first field or explicitly with something like appendSignIfNegative()