Foreign currency Reval on a zero balance GL

When we ran the foreign exchange revaluation program (FAGL_FC_VAL), a GL account with a zero balance was revaluated. Two line items with a debit & credit of the same amount were revaluated. I thought per standard functionality, nothing should have been revaluated when the balance is zero. When we posted the same transactions in a our regression environment and run the Reval program, nothing revaluated.

Thanks,