diff --git a/can/message.py b/can/message.py
index 57b61e34f..673bc3ca2 100644
--- a/can/message.py
+++ b/can/message.py
@@ -43,14 +43,14 @@ class Message(object):
         "is_fd",
         "bitrate_switch",
         "error_state_indicator",
-        "__weakref__", # support weak references to messages
-        "_dict" # see __getattr__
+        "__weakref__",              # support weak references to messages
+        "_dict"                     # see __getattr__
     )
 
     def __getattr__(self, key):
         # TODO keep this for a version, in order to not break old code
         # this entire method (as well as the _dict attribute in __slots__ and the __setattr__ method)
-        # can be removed in 3.0
+        # can be removed in 4.0
         # this method is only called if the attribute was not found elsewhere, like in __slots__
         try:
             warnings.warn("Custom attributes of messages are deprecated and will be removed in the next major version", DeprecationWarning)
@@ -68,20 +68,21 @@ def __setattr__(self, key, value):
 
     @property
     def id_type(self):
-        # TODO remove in 3.0
+        # TODO remove in 4.0
         warnings.warn("Message.id_type is deprecated, use is_extended_id", DeprecationWarning)
         return self.is_extended_id
 
     @id_type.setter
     def id_type(self, value):
-        # TODO remove in 3.0
+        # TODO remove in 4.0
         warnings.warn("Message.id_type is deprecated, use is_extended_id", DeprecationWarning)
         self.is_extended_id = value
 
-    def __init__(self, timestamp=0.0, arbitration_id=0, extended_id=True,
+    def __init__(self, timestamp=0.0, arbitration_id=0, is_extended_id=None,
                  is_remote_frame=False, is_error_frame=False, channel=None,
                  dlc=None, data=None,
                  is_fd=False, bitrate_switch=False, error_state_indicator=False,
+                 extended_id=True,
                  check=False):
         """
         To create a message object, simply provide any of the below attributes
@@ -99,7 +100,13 @@ def __init__(self, timestamp=0.0, arbitration_id=0, extended_id=True,
 
         self.timestamp = timestamp
         self.arbitration_id = arbitration_id
-        self.is_extended_id = extended_id
+        if is_extended_id is not None:
+            self.is_extended_id = is_extended_id
+        else:
+            if not extended_id:
+                # Passed extended_id=False (default argument is True) so we warn to update
+                warnings.warn("extended_id is a deprecated parameter, use is_extended_id", DeprecationWarning)
+            self.is_extended_id = extended_id
 
         self.is_remote_frame = is_remote_frame
         self.is_error_frame = is_error_frame
@@ -152,7 +159,7 @@ def __str__(self):
         if self.data is not None:
             for index in range(0, min(self.dlc, len(self.data))):
                 data_strings.append("{0:02x}".format(self.data[index]))
-        if data_strings: # if not empty
+        if data_strings:  # if not empty
             field_strings.append(" ".join(data_strings).ljust(24, " "))
         else:
             field_strings.append(" " * 24)
diff --git a/doc/message.rst b/doc/message.rst
index e7e9fb353..fcb5e5e1a 100644
--- a/doc/message.rst
+++ b/doc/message.rst
@@ -103,6 +103,7 @@ Message
         :type: bool
 
         This flag controls the size of the :attr:`~can.Message.arbitration_id` field.
+        Previously this was exposed as `id_type`.
 
         >>> print(Message(extended_id=False))
         Timestamp:        0.000000        ID: 0000    S        DLC: 0
@@ -110,8 +111,10 @@ Message
         Timestamp:        0.000000    ID: 00000000    X        DLC: 0
 
 
-        Previously this was exposed as `id_type`.
-        Please use `is_extended_id` from now on.
+        .. note::
+
+            The :meth:`Message.__init__` argument ``extended_id`` has been deprecated in favor of
+            ``is_extended_id``, but will continue to work for the ``3.x`` release series.
 
 
     .. attribute:: is_error_frame