diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 858cc44..a601c4f 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -6,7 +6,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.6", "3.x"]
       max-parallel: 6
 
     steps:
diff --git a/LICENSE b/LICENSE
index 2c4da26..13e8ed2 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2016-2023 Kenneth S. Kundert
+Copyright (c) 2016-2024 Kenneth S. Kundert
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/doc/conf.py b/doc/conf.py
index 4750fd5..c0468f0 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -51,7 +51,7 @@
 
 # General information about the project.
 project = u'quantiphy'
-copyright = u'2017-2023, Ken Kundert'
+copyright = u'2017-2024, Ken Kundert'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
diff --git a/doc/user.rst b/doc/user.rst
index 19f14c2..7948932 100644
--- a/doc/user.rst
+++ b/doc/user.rst
@@ -2739,11 +2739,6 @@ corresponding Python error for compatibility with existing code.  It is
 recommended that new code catch the *QuantiPhy* specific exceptions rather than 
 the generic Python exceptions as their use will be deprecated in the future.
 
-.. note::
-
-    It is expected that in release 2.20, expected in the first half of 2023, the 
-    exceptions will no longer inherit from the generic Python exceptions.
-
 *QuantiPhy* employs the following exceptions:
 
 :class:`ExpectedQuantity`:
diff --git a/quantiphy/quantiphy.py b/quantiphy/quantiphy.py
index 7f3698e..68ce8f5 100644
--- a/quantiphy/quantiphy.py
+++ b/quantiphy/quantiphy.py
@@ -22,7 +22,7 @@
 """
 
 # MIT License {{{1
-# Copyright (C) 2016-2023 Kenneth S. Kundert
+# Copyright (C) 2016-2024 Kenneth S. Kundert
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -1773,9 +1773,10 @@ def scale(self, scale, cls=None):
               the units, so the second argument is redundant and will eventually
               be deprecated.  The function returns two values, the value and
               units of the new value.
-            - If a string, it is taken to the be desired units. This value along
-              with the units of the quantity are used to select a known unit
-              conversion, which is applied to create the new value.
+            - If a string, it is taken to the be desired units, perhaps with a
+              scale factor. This value along with the units of the quantity are
+              used to select a known unit conversion, which is applied to create
+              the new value.
             - If a quantity, the units are ignored and the scale is treated as
               if were specified as a unitless float.
             - If a subclass of :class:`Quantity` that includes units, the units
@@ -1851,13 +1852,10 @@ def add(self, addend, check_units=False):
 
         try:
             if check_units and self.units != addend.units:
-                raise IncompatibleUnits(self.units, addend.units)
+                raise IncompatibleUnits(self, addend)
         except AttributeError:
             if check_units == 'strict':
-                raise IncompatibleUnits(
-                    getattr(self, 'units', None),
-                    getattr(addend, 'units', None)
-                )
+                raise IncompatibleUnits(self, addend)
         new = self.__class__(self.real + addend, self.units)
         new._inherit_attributes(self)
         return new
@@ -3424,7 +3422,7 @@ def convert(self, value=1, from_units=None, to_units=None):
                 elif from_units in self.to_units and value.units in self.to_units:
                     pass
                 else:
-                    raise IncompatibleUnits(value.units, from_units)
+                    raise IncompatibleUnits(value, from_units)
 
         if to_units is None and from_units is None:
             to_units = self.to_units[0]
diff --git a/quantiphy/quantiphy.pyi b/quantiphy/quantiphy.pyi
index 24575db..3c42b72 100644
--- a/quantiphy/quantiphy.pyi
+++ b/quantiphy/quantiphy.pyi
@@ -161,7 +161,7 @@ class Quantity(float):
         text: str,
         predefined: dict = ...,
         **kwargs,
-    ): ...
+    ) -> dict[str, Quantity]: ...
 
     @staticmethod
     def map_sf_to_sci_notation(sf: str): ...
diff --git a/tests/test_unit_conversion.py b/tests/test_unit_conversion.py
index deea70b..7dacff5 100644
--- a/tests/test_unit_conversion.py
+++ b/tests/test_unit_conversion.py
@@ -297,11 +297,11 @@ def test_add():
 
     with pytest.raises(IncompatibleUnits) as exception:
         total = total.add(Quantity(contribution, 'lbs'), check_units=True)
-    assert str(exception.value) == "incompatible units ($ and lbs)."
+    assert str(exception.value) == "incompatible units ($44.04 and 9.89 lbs)."
     assert isinstance(exception.value, IncompatibleUnits)
     assert isinstance(exception.value, QuantiPhyError)
     assert isinstance(exception.value, TypeError)
-    assert exception.value.args == ('$', 'lbs')
+    assert "{} and {}".format(*exception.value.args) == "$44.04 and 9.89 lbs"
 
 def test_linear_conversion():
     Quantity.reset_prefs()
diff --git a/tox.ini b/tox.ini
index 92a8f1a..c914ca4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,7 +3,9 @@ envlist = lint, pytest, mypy
 isolated_build = True
 
 [testenv:lint]
-deps = pylama
+deps =
+    setuptools
+    pylama
 skip_install = true
 commands = pylama --ignore E226,E501,C901,E116,E251,E203 quantiphy/*.py