diff --git a/cryptography/hazmat/primitives/padding.py b/cryptography/hazmat/primitives/padding.py
index ddb2c63..1717262 100644
--- a/cryptography/hazmat/primitives/padding.py
+++ b/cryptography/hazmat/primitives/padding.py
@@ -86,8 +86,7 @@
 class _PKCS7PaddingContext(object):
     def __init__(self, block_size):
         self.block_size = block_size
-        # TODO: O(n ** 2) complexity for repeated concatentation, we should use
-        # zero-buffer (#193)
+        # TODO: more copies than necessary, we should use zero-buffer (#193)
         self._buffer = b""
 
     def update(self, data):
@@ -120,8 +119,7 @@
 class _PKCS7UnpaddingContext(object):
     def __init__(self, block_size):
         self.block_size = block_size
-        # TODO: O(n ** 2) complexity for repeated concatentation, we should use
-        # zero-buffer (#193)
+        # TODO: more copies than necessary, we should use zero-buffer (#193)
         self._buffer = b""
 
     def update(self, data):