Boolean solid in Parameterised Volume

Hi,

I’m trying to write a geometry to a GDML file, using the G4GDMLParser->Write() function, but I keep running into an error.
My simulation world contains a paramererised volume, consisting of copies of a union solid.
The union solid is just a sphere in union with a cylinder.

The geometry builds without problems, but once I try to write the geometry to a GDML file, I get this error:
G4GDML: Writing setup…

-------- EEEE ------- G4Exception-START -------- EEEE -------
*** G4Exception : InvalidSetup
      issued by : G4GDMLWriteParamvol::ParametersWrite()
Solid 'bumps_detector1' cannot be used in parameterised volume!
*** Fatal Exception *** core dump ***
 **** Track information is not available at this moment
 **** Step information is not available at this moment

-------- EEEE -------- G4Exception-END --------- EEEE -------


*** G4Exception: Aborting execution ***
Aborted (core dumped)

Could anyone help me fix this problem?

Cheers,
Koen