Nucleus with Z < 0 produced

[saikatxdas]

I am running a 1D simulation with injected Helium particles from a source redshift evolution and with relevant interactions for energy loss. The simulation fails with following Exception error saying that particle with negative atomic and mass number is produced.

crpropa::ModuleList: Number of Threads: 8
Run ModuleList
Exception in crpropa::ModuleList::run: =>       ]  25%    Finish in: 01:49:48 
crpropa::Nucleus: no nucleus with Z < 0, A=-30 Z=-14

Can someone please tell me, what are the possible causes for this?