diff --git a/bonobo/util/iterators.py b/bonobo/util/iterators.py
index 82f8518..04c81a5 100644
--- a/bonobo/util/iterators.py
+++ b/bonobo/util/iterators.py
@@ -38,6 +38,6 @@ def tuplize(generator):
 
 
 def iter_if_not_sequence(mixed):
-    if isinstance(mixed, (dict, list, str)):
+    if isinstance(mixed, (dict, list, str, bytes, )):
         raise TypeError(type(mixed).__name__)
     return iter(mixed)