diff --git a/zipline/finance/trading.py b/zipline/finance/trading.py
index 828ae7e9..9f64db97 100644
--- a/zipline/finance/trading.py
+++ b/zipline/finance/trading.py
@@ -96,7 +96,6 @@ class TradingEnvironment(object):
         self.open_and_closes = env_trading_calendar.open_and_closes.loc[
             self.trading_days]
 
-        self.prev_environment = self
         self.bm_symbol = bm_symbol
         if not load:
             load = load_market_data