diff --git a/tests/finance/test_slippage.py b/tests/finance/test_slippage.py
index c4feaaec..f6f8d4c0 100644
--- a/tests/finance/test_slippage.py
+++ b/tests/finance/test_slippage.py
@@ -69,7 +69,8 @@ class SlippageTestCase(TestCase):
             'dt': datetime.datetime(
                 2006, 1, 5, 14, 31, tzinfo=pytz.utc),
             'amount': int(50),
-            'sid': int(133)
+            'sid': int(133),
+            'commission': None
         }
 
         self.assertIsNotNone(txn)
diff --git a/tests/test_perf_tracking.py b/tests/test_perf_tracking.py
index c75646fe..fab97cfe 100644
--- a/tests/test_perf_tracking.py
+++ b/tests/test_perf_tracking.py
@@ -24,7 +24,7 @@ from operator import attrgetter
 
 import zipline.utils.factory as factory
 import zipline.finance.performance as perf
-from zipline.utils.protocol_utils import ndict
+from zipline.finance.slippage import Transaction
 
 from zipline.gens.composites import date_sorted_sources
 from zipline.finance.trading import SimulationParameters
@@ -1018,7 +1018,7 @@ class TestPerformanceTracker(unittest.TestCase):
         #create a transaction for all but
         #first trade in each sid, to simulate None transaction
         if event.dt != no_txn_dt:
-            txn = ndict({
+            txn = Transaction(**{
                 'sid': event.sid,
                 'amount': -25,
                 'dt': event.dt,
diff --git a/zipline/finance/slippage.py b/zipline/finance/slippage.py
index 20653aaa..ef85f645 100644
--- a/zipline/finance/slippage.py
+++ b/zipline/finance/slippage.py
@@ -50,9 +50,12 @@ def transact_partial(slippage, commission):
 
 class Transaction(object):
 
-    def __init__(self, initial_values=None):
-        if initial_values:
-            self.__dict__ = initial_values
+    def __init__(self, sid, amount, dt, price, commission=None):
+        self.sid = sid
+        self.amount = amount
+        self.dt = dt
+        self.price = price
+        self.commission = commission
 
     def __getitem__(self, name):
         return self.__dict__[name]
@@ -67,7 +70,7 @@ def create_transaction(sid, amount, price, dt):
         'price': price,
     }
 
-    transaction = Transaction(txn)
+    transaction = Transaction(**txn)
     return transaction