TChain Draw() User function with Proof-lite fails

ROOT
1

Dear all,

I am trying to call a user function in a TChain.Draw() context with Proof enabled and it seems to fail.

Basically I have a TChain containing multiple files with multiple TTrees. these are all friended to an empty Tree and Proof is enabled.

It works fantastically well until I try to use my own function inside the TFormula.

I specify something simple like:

double getl(double x=0){
   return 42.0;
}
mastertree->Draw("getl(friendtree.value)")

which produces this error:

If i disable Proof it works…

The code is a bit entangled, but I can send it on demand.

Best,
Morten