diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f5b3e9ba..c83850c3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,20 +26,20 @@ jobs:
             python-version: 3.9
             toxenv: py39
 
-          - name: Python 3.8
+          - name: Python 3.12
             runs-on: ubuntu-latest
-            python-version: 3.8
-            toxenv: py38
+            python-version: 3.12
+            toxenv: py312
 
           - name: Code style checks
             runs-on: ubuntu-latest
-            python-version: 3.8
+            python-version: 3.11
             toxenv: style
 
-          - name: Python 3.8 with dev dependencies
+          - name: Python 3.11 with dev dependencies
             runs-on: ubuntu-latest
-            python-version: 3.8
-            toxenv: py38-dev
+            python-version: 3.11
+            toxenv: dev
     steps:
       - uses: actions/checkout@v2
         with:
@@ -67,10 +67,10 @@ jobs:
       - uses: actions/checkout@v2
         with:
           fetch-depth: 0
-      - name: Set up Python 3.8
+      - name: Set up Python 3.11
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.11
       - name: Install tox
         run: |
           python -m pip install --upgrade pip
diff --git a/.readthedocs.yml b/.readthedocs.yml
index 0e8f7817..0b865ca0 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -1,15 +1,30 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
 version: 2
 
 sphinx:
   builder: html
   configuration: doc/source/conf.py
+  fail_on_warning: true
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: mambaforge-4.10
+
+conda:
+  environment: doc/rtd_requirements.yaml
 
 python:
-  version: 3.8
-  system_packages: true
   install:
     - method: pip
       path: .
+      extra_requirements:
+        - doc
+
 
 # Don't build any extra formats
 formats: []
diff --git a/MANIFEST.in b/MANIFEST.in
index 19a62f2a..cb99df43 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,2 +1 @@
-include RELIC-INFO
 exclude stwcs/version.py
diff --git a/doc/rtd-pip-requirements b/doc/rtd-pip-requirements
deleted file mode 100644
index e5f235d7..00000000
--- a/doc/rtd-pip-requirements
+++ /dev/null
@@ -1,2 +0,0 @@
-numpy>=1.11
-astropy
diff --git a/doc/rtd_requirements.yaml b/doc/rtd_requirements.yaml
new file mode 100644
index 00000000..c1512bc5
--- /dev/null
+++ b/doc/rtd_requirements.yaml
@@ -0,0 +1,9 @@
+name: rtd311
+
+dependencies:
+ - python=3.11
+ - numpy
+ - astropy
+ - pip
+ - graphviz
+ - sphinx_rtd_theme>1.2.0
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 6c323d17..9b18616c 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -15,6 +15,7 @@
 import importlib
 # Check Sphinx version
 import sphinx
+import sphinx_rtd_theme
 
 
 # If extensions (or modules to document with autodoc) are in another directory,
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 37adcf65..6c2f308a 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,2 +1,7 @@
-git+https://github.com/astropy/astropy.git
 git+https://github.com/spacetelescope/stsci.tools.git
+
+--extra-index-url https://pypi.anaconda.org/astropy/simple https://pypi.anaconda.org/liberfa/simple https://pypi.anaconda.org/scientific-python-nightly-wheels/simple astropy --pre
+
+# Use Bi-weekly numpy/scipy dev builds
+--extra-index-url https://pypi.anaconda.org/scientific-python-nightly-wheels/simple
+numpy>=0.0.dev0
diff --git a/setup.cfg b/setup.cfg
index 29ad9073..c97f4742 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -9,8 +9,8 @@ edit_on_github = False
 github_project = spacetelescope/stwcs
 
 [tool:pytest]
-minversion = 3.6
-norecursedirs = build docs/_build relic
+minversion = 3.9
+norecursedirs = build docs/_build
 filterwarnings=
   ignore:.*Card is too long*
   ignore:.*Some non-standard WCS keywords*
@@ -22,6 +22,11 @@ filterwarnings=
 builder = html
 warning-is-error = 1
 
+[options.extras_require]
+docs =
+    sphinx
+    sphinx-rtd-theme
+
 [flake8]
 # E402, E501, E722 should be added back to the selection list
 # once they are made to pass.
diff --git a/setup.py b/setup.py
index 00c47db6..e16656d2 100755
--- a/setup.py
+++ b/setup.py
@@ -3,11 +3,6 @@
 from setuptools import setup, find_packages
 from configparser import ConfigParser
 
-if sys.version_info < (3, 6):
-    error = """
-    STWCS supports Python 3.6 and above.
-    """
-    sys.exit(error)
 
 conf = ConfigParser()
 conf.read(['setup.cfg'])
diff --git a/stwcs/__init__.py b/stwcs/__init__.py
index 8e39881f..a2465961 100644
--- a/stwcs/__init__.py
+++ b/stwcs/__init__.py
@@ -14,18 +14,19 @@
 
 """
 import os
+import importlib.metadata
 
 from . import distortion  # noqa
 from stsci.tools import fileutil  # noqa
 from stsci.tools import teal  # noqa
 
-from pkg_resources import get_distribution, DistributionNotFound
 
 try:
-    __version__ = get_distribution(__name__).version
-except DistributionNotFound:
+    __version__ = importlib.metadata.version(__name__)
+
+except importlib.metadata.PackageNotFoundError:  # pragma: no cover
     # package is not installed
-    pass
+    pass  # pragma: no cover
 
 try:
     from . import gui
diff --git a/stwcs/tests/test_updatewcs.py b/stwcs/tests/test_updatewcs.py
index b227e994..c6bc51b4 100644
--- a/stwcs/tests/test_updatewcs.py
+++ b/stwcs/tests/test_updatewcs.py
@@ -1,8 +1,10 @@
 import shutil
 import os
+import warnings
 
 from astropy import wcs
 from astropy.io import fits
+from astropy.wcs import FITSFixedWarning
 from .. import updatewcs
 from ..updatewcs import apply_corrections
 from ..distortion import utils as dutils
@@ -11,8 +13,9 @@
 from numpy import testing
 import pytest
 
-
 from . import data
+
+
 data_path = os.path.split(os.path.abspath(data.__file__))[0]
 
 os.environ['ASTROMETRY_STEP_CONTROL'] = 'Off'
@@ -464,6 +467,9 @@ def test_update_stis_asn():
     shutil.copyfile(stis_asn_orig_file, fname)
     shutil.copyfile(idc_orig_file, idctab)
 
+    warnings.simplefilter("ignore", category=FITSFixedWarning)#,
+                          #  message=" 'datfix' made the change 'Set MJD-OBS to 50853.000000 from DATE-OBS'.")
+
     expnames = updatewcs.updatewcs(fname)
 
     assert expnames[0] == os.path.basename(fname_expname1)
diff --git a/stwcs/updatewcs/corrections.py b/stwcs/updatewcs/corrections.py
index 7dec5686..67349c1f 100644
--- a/stwcs/updatewcs/corrections.py
+++ b/stwcs/updatewcs/corrections.py
@@ -348,8 +348,8 @@ def updateWCS(cls, ext_wcs, ref_wcs):
                 if n >= m and n >= 2:
                     idcval = np.array([[cx[n, m]], [cy[n, m]]])
                     sipval = np.dot(imatr, idcval)
-                    akeys1[m, n - m] = sipval[0]
-                    bkeys1[m, n - m] = sipval[1]
+                    akeys1[m, n - m] = sipval[0].item()
+                    bkeys1[m, n - m] = sipval[1].item()
                     Akey = "A_%d_%d" % (m, n - m)
                     Bkey = "B_%d_%d" % (m, n - m)
                     kw2update[Akey] = sipval[0, 0] * ext_wcs.binned, sip_comment
diff --git a/tox.ini b/tox.ini
index d7dd5a58..e151a5f7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,12 +1,17 @@
 [tox]
-envlist= py38, py310, style
+envlist= py311, py312, py310, style, dev
 
 [testenv]
-deps=
-    dev: -rrequirements-dev.txt
+
+set_env =
+    dev: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/astropy/simple https://pypi.anaconda.org/liberfa/simple https://pypi.anaconda.org/scientific-python-nightly-wheels/simple
+
+commands_pre =
+   dev: pip install -r requirements-dev.txt -U --upgrade-strategy eager
+   
 extras= test
-# astropy will complain if the home directory is missing
-passenv= HOME
+
+
 commands=
     pytest