BiddingScheme - Bidding scheme object set to None for Target Impression Share bidding strategy

Hello,

I have a problem when I get the campaign data for a certain type of bidding strategy using the "GetCampaignsByAccountId" method.
"Target impression Share" and "Maximize Conversion Value" only return None while I get the correct BiddingScheme object for other strategies.

For instance :

Getting information about the bidding scheme of a target ROAS campaign gives me this :

(TargetRoasBiddingScheme){

Type = "TargetRoasBiddingScheme"

MaxCpc =

(Bid){

Amount = 1.1

}

TargetRoas = 22.0

}

When I call the API for a "Target impression Share" or "Maximize Conversion Value" campaigns we have this : 

None

Do you have any clue about what's wrong here ?

Thanks