diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 38e10240..2dc9a714 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -5,10 +5,14 @@ on: [push]
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
+        os: [ubuntu-latest]
         python-version: ["3.7", "3.8", "3.9", "3.10"]
+        include:
+          - os: macos-latest
+            python-version: "3.10"
 
     steps:
     - uses: actions/checkout@v2
@@ -16,6 +20,11 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
+
+    - name: Install MacOS dependencies
+      if: matrix.os == 'macos-latest'
+      run: brew install gsl
+
     - name: Install dependencies
       run: |
         python -m pip install -U pip
diff --git a/CHANGES.rst b/CHANGES.rst
index fae147dd..e8c77cd9 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,13 @@
 Changelog
 =========
 
+1.3.1 (upcoming)
+----------------
+
+Enhancements
+~~~~~~~~~~~~
+- Add support for MacOS and add CI config [#59]
+
 1.3.0 (2022-06-08)
 ------------------
 
diff --git a/abacusnbody/common.py b/abacusnbody/common.py
new file mode 100644
index 00000000..a926d143
--- /dev/null
+++ b/abacusnbody/common.py
@@ -0,0 +1,17 @@
+'''Common utility functions.
+'''
+
+def maxthreads():
+    '''Return the number of logical cores available to this process.
+    First tries the affinity mask, then the total number of CPUs,
+    then 1 if all else fails.
+    '''
+    import multiprocessing
+    import os
+    
+    try:
+        maxthreads = len(os.sched_getaffinity(0))
+    except AttributeError:
+        maxthreads = multiprocessing.cpu_count() or 1
+        
+    return maxthreads
diff --git a/abacusnbody/data/compaso_halo_catalog.py b/abacusnbody/data/compaso_halo_catalog.py
index 873e91d7..951bb1c9 100644
--- a/abacusnbody/data/compaso_halo_catalog.py
+++ b/abacusnbody/data/compaso_halo_catalog.py
@@ -290,10 +290,11 @@
     raise Exception("Abacus ASDF extension not properly loaded! Try reinstalling abacusutils, or updating ASDF: `pip install asdf>=2.8`") from e
 
 from . import bitpacked
+from ..common import maxthreads
 
 # Default to 4 decompression threads, or fewer if fewer cores are available
 DEFAULT_BLOSC_THREADS = 4
-DEFAULT_BLOSC_THREADS = max(1, min(len(os.sched_getaffinity(0)), DEFAULT_BLOSC_THREADS))
+DEFAULT_BLOSC_THREADS = max(1, min(maxthreads(), DEFAULT_BLOSC_THREADS))
 from . import asdf as _asdf
 _asdf.set_nthreads(DEFAULT_BLOSC_THREADS)
 
@@ -1741,4 +1742,3 @@ def unpack_euler16(bin_this):
                     ('sigmavtan_L2com', np.float32),
                     ('rvcirc_max_L2com', np.float32),
 ], align=True)
- 
diff --git a/setup.py b/setup.py
index 19cbc38b..0a54b576 100644
--- a/setup.py
+++ b/setup.py
@@ -1,6 +1,6 @@
 import os
 
-from setuptools import setup, find_namespace_packages
+from setuptools import setup, find_packages
 
 install_requires = ['numpy>=1.16','blosc>=1.9.2','astropy>=4.0.0','scipy>=1.5.0','numba>=0.50','asdf>=2.8','h5py','pyyaml']
 
@@ -27,7 +27,7 @@
     long_description=long_description,
     long_description_content_type="text/markdown",
     url="https://github.com/abacusorg/abacusutils",
-    packages=find_namespace_packages(include=['abacusnbody.*']),
+    packages=find_packages(include=['abacusnbody']),
     include_package_data=True,
     classifiers=[
         "Programming Language :: Python :: 3",