diff --git a/cvxportfolio/simulator.py b/cvxportfolio/simulator.py
index 0910fc9ea..ebf2403a9 100644
--- a/cvxportfolio/simulator.py
+++ b/cvxportfolio/simulator.py
@@ -200,7 +200,7 @@ def simulate(self, t, t_next, h, policy, past_returns, current_returns,
             u = self._round_trade_vector(u, current_prices)
 
         # recompute cash
-        u.iloc[-1] = sum(u.iloc[:-1])
+        u.iloc[-1] = -sum(u.iloc[:-1])
         assert sum(u) == 0.
 
         # compute post-trade holdings (including cash balance)