diff --git a/zipline/transforms/utils.py b/zipline/transforms/utils.py
index c8a431e1..59f40cb8 100644
--- a/zipline/transforms/utils.py
+++ b/zipline/transforms/utils.py
@@ -463,11 +463,17 @@ class BatchTransform(object):
 
         #################################################
         # Determine whether we should call the transform
+        # 0. Support historical/legacy usage of '0' signaling,
+        #    'update on every bar'
+        if self.refresh_period == 0:
+            period_signals_update = True
+        else:
         # 1. Is the refresh period over?
-        period_over = self.trading_days_total % self.refresh_period == 0
+            period_signals_update = (
+                self.trading_days_total % self.refresh_period == 0)
         # 2. Have the args or kwargs been changed since last time?
         args_updated = args != self.last_args or kwargs != self.last_kwargs
-        recalculate_needed = args_updated or (period_over and
+        recalculate_needed = args_updated or (period_signals_update and
                                               self.updated)
 
         if recalculate_needed: