Classic: IsRaidMarkerActive() error?

[Zax]

Hello,

I use IsRaidMarkerActive(), found in Blizzard_CompactRaidFrame 8.2.5 / FrameManager.lua, without problem on the 8.2.5 version, but it causes the following lua error on Classic:

attempt to call global 'IsRaidMarkerActive' (a nil value)

Any idea of what is wrong?

Thank you.