diff --git a/zipline/gens/composites.py b/zipline/gens/composites.py
index 964bbe42..af2fdc8c 100644
--- a/zipline/gens/composites.py
+++ b/zipline/gens/composites.py
@@ -18,15 +18,15 @@ def date_sorted_sources(*sources):
     """
 
     for source in sources:
-        assert source.__dict__.has_key('__init__')
-        assert source.__dict__.has_key('get_hash')
+        assert iter(source), "Source %s not iterable" % source
+        assert source.__class__.__dict__.has_key('get_hash'), "No get_hash"
 
     # Get name hashes to pass to date_sort.
-    names = [source.get_hash for source in sources)
+    names = [source.get_hash() for source in sources]
 
     # Convert the list of generators into a flat stream by pulling
     # one element at a time from each.
-    stream_in = roundrobin(source_gens, names)
+    stream_in = roundrobin(sources, names)
     
     # Guarantee the flat stream will be sorted by date, using source_id as
     # tie-breaker, which is fully deterministic (given deterministic string 
diff --git a/zipline/gens/examples.py b/zipline/gens/examples.py
index 93f77d47..5a24493f 100644
--- a/zipline/gens/examples.py
+++ b/zipline/gens/examples.py
@@ -23,7 +23,7 @@ if __name__ == "__main__":
         'delta'  : timedelta(minutes = 1),
         'filter' : filter
     }
-    bundle_a = SourceBundle(SpecificEquityTrades, args_a, kwargs_a)
+    source_a = SpecificEquityTrades(*args_a, **kwargs_a)
 
     #Set up source b. Two minutes between events.
     args_b = tuple()
@@ -33,12 +33,12 @@ if __name__ == "__main__":
         'delta'  : timedelta(minutes = 1),
         'filter' : filter
     }
-    bundle_b = SourceBundle(SpecificEquityTrades, args_b, kwargs_b)
+    source_b = SpecificEquityTrades(*args_b, **kwargs_b)
 
     #Set up source c. Three minutes between events.
 
     sort_out = date_sorted_sources(source_a, source_b)     
-
+    
 #     passthrough = TransformBundle(Passthrough, (), {})
 #     mavg_price = TransformBundle(MovingAverage, (timedelta(minutes = 20), ['price']), {})
 #     tnfm_bundles = (passthrough, mavg_price)