Negative balance

After renewing a merc's contract I ended up with a negative balance. This happened because the merc (Shadow) had a life insurance. I had a balance of $39k and some bucks. The contract for two weeks cost exactly $39k. But the insurance was like ~$1000 additionally. I guess, it shouldn't be possible for the player to get a negative balance. I'm not sure, but this might be an issue from vanilla JA2?!