diff --git a/rlp/sedes/binary.py b/rlp/sedes/binary.py
index <HASH>..<HASH> 100644
--- a/rlp/sedes/binary.py
+++ b/rlp/sedes/binary.py
@@ -16,9 +16,9 @@ class Binary(object):
         self.allow_empty = allow_empty
 
     @classmethod
-    def fixed_length(cls, l):
+    def fixed_length(cls, l, allow_empty=False):
         """Create a sedes for binary data with exactly `l` bytes."""
-        return cls(l, l)
+        return cls(l, l, allow_empty=allow_empty)
 
     def is_valid_length(self, l):
         return any((self.min_length <= l <= self.max_length,
diff --git a/rlp/sedes/lists.py b/rlp/sedes/lists.py
index <HASH>..<HASH> 100644
--- a/rlp/sedes/lists.py
+++ b/rlp/sedes/lists.py
@@ -80,7 +80,7 @@ class Serializable(object):
     :param \*args: initial values for the first attributes defined via
                   :attr:`fields`
     :param \*\*kwargs: initial values for all attributes not initialized via
-                     positional arguments
+                       positional arguments
     """
 
     fields = tuple()
Added allow_empty option for fixed_length binary