diff --git a/src/bits.py b/src/bits.py
index 219c612..b34d5be 100644
--- a/src/bits.py
+++ b/src/bits.py
@@ -935,7 +935,7 @@ class Bytes:
 
     import sys
 
-    def __init__(self, var=None, byteorder="big"):
+    def __init__(self, var=None, byteorder="big", bits=None):
         """
         var: a supported variant (object)
         byteorder: notimplemented, mostly ignored
@@ -943,11 +943,17 @@ class Bytes:
         self.__raw = bytearray(b'')
         self.__small = False
         self.__iter = None
-        self.__list_len = None
+        self.__bit_len = None
         if byteorder.lower() in ["small", "little"]:
             self.__small = True
         if var is not None:
             self.__raw = self.__to_bytearray(var)
+        if bits is None:
+            self.__bit_len = len(self.__raw)
+        else:
+            if not isinstance(bits, (int, Bytes, Bit)):
+                raise TypeError(f"bits argument must be int, not {type(bits)}")
+            self.__bit_len = int(bits)
 
     def __bytes__(self):
         """