diff --git a/zipline/errors.py b/zipline/errors.py
index c7859b49..0f75bd6b 100644
--- a/zipline/errors.py
+++ b/zipline/errors.py
@@ -104,6 +104,15 @@ Transaction {txn} not in same direction as corresponding order {order}.
 
 
 class TransactionWithNoAmount(ZiplineError):
+    """
+    Raised if a transact call returns a transaction with zero amount.
+    """
+    msg = """
+Transaction {txn} has an amount of zero.
+""".strip()
+
+
+class TransactionVolumeExceedsOrder(ZiplineError):
     """
     Raised if a transact call returns a transaction with a volume greater than
 the corresponding order.