diff --git a/README.md b/README.md
index f591be911571b25a6633673c6ac676c015ef85da..839bdfc734fad3c372a2ce457ab64f7f55bec09c 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ Satella is a zero-requirements Python 3.5+ library for writing
 server applications, especially those dealing with mundane but
 useful things. It also runs on PyPy.
 
-See [LICENSE](LICENSE) for text of the license.
+See [LICENSE](LICENSE) for text of the license. This library may contain
+code taken from elsewhere on the internets, so this is copyright (c) respective authors.
 
 **satella 1.0 remains in [maintenance mode](https://github.com/piotrmaslanka/satella/tree/satella1.0)**
diff --git a/satella/coding/structures/immutable.py b/satella/coding/structures/immutable.py
index b06a92d465bfaa35323846f035d2178e46ed7796..bcc08203a7f412f85402e3cbef511c8a3da16e0b 100644
--- a/satella/coding/structures/immutable.py
+++ b/satella/coding/structures/immutable.py
@@ -10,7 +10,7 @@ class ImmutableMetaType(ABCMeta):
         return p
 
 
-class Immutable:
+class Immutable(metaclass=ImmutableMetaType):
     """
     A mix-in to make your classes immutable.
 
@@ -20,7 +20,6 @@ class Immutable:
     >>>     def __init__(self):
     >>>         self.attribute = 'value'
     """
-    __metaclass__ = ImmutableMetaType
 
     __locked_for_writes = False