diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03b2a8d..5be5c45 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -45,6 +45,7 @@ jobs:
           - "3.9"
           - "3.10"  # not 3.10 which truncates to 3.1
           - "3.11"
+          - "3.12"
       max-parallel: 5
 
     steps:
@@ -68,6 +69,7 @@ jobs:
 
     - name: Run tests with pytest & coverage
       run: |
+        set -vxeuo pipefail
         coverage run --concurrency=thread --parallel-mode -m pytest -vvv .
         coverage combine
         coverage report --precision 3
diff --git a/CHANGES.rst b/CHANGES.rst
index 9971eb9..0037940 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -20,10 +20,20 @@ Change History
 
    release expected TBA
 
-    1.0.6 (developing)
-    ******************
+1.0.6 (developing)
+******************
 
-    release expected TBA
+release expected TBA
+
+Fixes
+--------------
+
+* Fixed *math domain error* in standard deviation functions.
+
+Maintenance
+--------------
+
+* Add Python 3.12
 
 1.0.5
 ******
diff --git a/pyproject.toml b/pyproject.toml
index c124e5a..792da1b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,10 +1,10 @@
 [build-system]
-requires = ["setuptools>=45", "setuptools_scm[toml]>=6.2"]
+requires = ["setuptools>=61", "setuptools_scm[toml]>=8"]
 build-backend = "setuptools.build_meta"
 
 [tool.black]
 line-length = 115
-target-version = ['py311']
+target-version = ['py312']
 include = '\.pyi?$'
 exclude = '''
 
diff --git a/pysumreg/__init__.py b/pysumreg/__init__.py
index 46f5f67..6d254aa 100644
--- a/pysumreg/__init__.py
+++ b/pysumreg/__init__.py
@@ -18,7 +18,7 @@
 # -----------------------------------------------------------------------------
 # :author:    Pete R. Jemian
 # :email:     prjemian@gmail.com
-# :copyright: (c) 2014-2022, Pete R. Jemian
+# :copyright: (c) 2014-2024, Pete R. Jemian
 #
 # Distributed under the terms of the Creative Commons Attribution 4.0 International Public License.
 #
diff --git a/pysumreg/sum_registers.py b/pysumreg/sum_registers.py
index 28a0278..ee0f8b7 100644
--- a/pysumreg/sum_registers.py
+++ b/pysumreg/sum_registers.py
@@ -180,7 +180,9 @@ def stddev_x(self):
 
         .. math:: \sigma_x^2 = {{\sum{x^2} - \bar{x}\sum{x}} \over {n-1}}
         """
-        return math.sqrt((self.XX - self.mean_x * self.X) / (self.n - 1))
+        numerator = max(0, self.XX - self.mean_x * self.X)
+        denominator = self.n - 1
+        return math.sqrt(numerator / denominator)
 
     @property
     def stddev_y(self):
@@ -189,7 +191,9 @@ def stddev_y(self):
 
         .. math:: \sigma_y^2 = {{\sum{y^2} - \bar{y}\sum{y}} \over {n-1}}
         """
-        return math.sqrt((self.YY - self.mean_y * self.Y) / (self.n - 1))
+        numerator = max(0, self.YY - self.mean_y * self.Y)
+        denominator = self.n - 1
+        return math.sqrt(numerator / denominator)
 
     @property
     def slope(self):
diff --git a/setup.cfg b/setup.cfg
index e29b72c..9ef9abb 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -29,7 +29,7 @@ profile=black
 
 [metadata]
 name = pysumreg
-copyright = 2022-2022, Pete R. Jemian
+copyright = 2014-2024, Pete R. Jemian
 description = Statistics of list of (x, y) pairs from calculator-style summation registers.
 description_file = README.md
 description_file_content_type = text/markdown
@@ -54,6 +54,7 @@ classifiers =
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
+    Programming Language :: Python :: 3.12
     Topic :: Scientific/Engineering
     Topic :: Scientific/Engineering :: Astronomy
     Topic :: Scientific/Engineering :: Bio-Informatics
@@ -70,7 +71,7 @@ classifiers =
 # python_requires = >=3.8
 packages = find:
 setup_requires =
-    setuptools_scm[toml]>=6.2
+    setuptools_scm[toml]>=8
 
 # Specify any package dependencies below.  Examples shown
 # None
diff --git a/setup.py b/setup.py
index 5266a05..fd0bef4 100755
--- a/setup.py
+++ b/setup.py
@@ -12,7 +12,7 @@
 # -----------------------------------------------------------------------------
 # :author:    Pete R. Jemian
 # :email:     prjemian@gmail.com
-# :copyright: (c) 2014-2022, Pete R. Jemian
+# :copyright: (c) 2014-2024, Pete R. Jemian
 #
 # Distributed under the terms of the Creative Commons Attribution 4.0 International Public License.
 #