diff --git a/zipline/sources/simulated.py b/zipline/sources/simulated.py
index 66c4f679e..e25a429b4 100644
--- a/zipline/sources/simulated.py
+++ b/zipline/sources/simulated.py
@@ -93,9 +93,6 @@ def __init__(self, start_prices=None, freq='minute', start=None,
         self.sd = sd
 
         self.sids = self.start_prices.keys()
-        TradingEnvironment.instance().write_data(
-            equities_identifiers=self.sids
-        )
 
         self.open_and_closes = \
             calendar.open_and_closes[self.start:self.end]
diff --git a/zipline/sources/test_source.py b/zipline/sources/test_source.py
index 512309cd6..278940c0d 100644
--- a/zipline/sources/test_source.py
+++ b/zipline/sources/test_source.py
@@ -136,7 +136,6 @@ def __init__(self, env=None, *args, **kwargs):
                 'sids',
                 set(event.sid for event in self.event_list)
             )
-            env.write_data(equities_identifiers=self.identifiers)
             assets_by_identifier = {}
             for identifier in self.identifiers:
                 assets_by_identifier[identifier] = env.asset_finder.\
@@ -160,7 +159,6 @@ def __init__(self, env=None, *args, **kwargs):
             self.concurrent = kwargs.get('concurrent', False)
 
             self.identifiers = kwargs.get('sids', [1, 2])
-            env.write_data(equities_identifiers=self.identifiers)
             assets_by_identifier = {}
             for identifier in self.identifiers:
                 assets_by_identifier[identifier] = env.asset_finder.\
diff --git a/zipline/utils/factory.py b/zipline/utils/factory.py
index 17fca76ea..628f0f3f4 100644
--- a/zipline/utils/factory.py
+++ b/zipline/utils/factory.py
@@ -119,7 +119,6 @@ def create_trade_history(sid, prices, amounts, interval, sim_params,
                          source_id="test_factory"):
     trades = []
     current = sim_params.first_open
-    trading.environment.write_data(equities_identifiers=[sid])
 
     oneday = timedelta(days=1)
     use_midnight = interval >= oneday
@@ -311,8 +310,6 @@ def create_test_df_source(sim_params=None, bars='daily'):
 
     df = pd.DataFrame(x, index=index, columns=[0])
 
-    trading.environment.write_data(equities_identifiers=[0])
-
     return DataFrameSource(df), df