Formatter bug: "/=" after "else" in "case"

[konovod]

scale = 0
a = 0
case scale
when 0
  a = 0
else
  a /= 2
end

This code compiles and runs, but formatter fails to format it. Failing line is a /= 2, other are included just to make code correct. a /= 2 in when 0 section doesn't cause fail, neither do a /= 2 in if-else sections, only in case-else. a *= 2 doesn't fails too, so this is perhaps some of those "is not a regexp" things.