Custom rule using lookbehind becomes Invalid configuration

[asa08]

I want to use lookbehind in a custom rule but get Invalid configuration for 'xxx'. Falling back to default.. Is there any other way?

Example

No setClass on the line before the line containing configur.

(?<!setClass.*?\n.*?)configur

Highlighted

func setup() {
  configur()
}

Not Highlighted

func setup() {
  setClass()
  configur()
}

Thank you.