diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 2428925..df40935 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,37 +1,37 @@
 # CI python workflow
 name: CI
 
-# Controls when the action will run. 
+# Controls when the action will run.
 on:
   # Triggers the workflow on push or pull request events but only for the master branch
   push:
-    branches: [ master ]
+    branches: [master]
   pull_request:
-    branches: [ master ]
+    branches: [master]
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
 
 jobs:
   build:
-    
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        os: [macos-latest]
+        python: [3.7, 3.8]
 
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
-      - name: Set up Python ${{ matrix.python-version }}
+      - name: Set up Python ${{ matrix.python }}
         uses: actions/setup-python@v2
         with:
-          python-version: ${{ matrix.python-version }}
+          python-version: ${{ matrix.python }}
       - name: Install dependencies
         run: |
           pip install -q --upgrade pip
           pip install -q -r requirements.txt
           pip install -q --upgrade codecov coverage black flake8 codacy-coverage
-      - name: Lint & format
+      - name: Lint
         run: |
           black --check --diff stree
           flake8 --count stree
@@ -49,4 +49,3 @@ jobs:
         with:
           project-token: ${{ secrets.CODACY_PROJECT_TOKEN }}
           coverage-reports: coverage.xml
-        
diff --git a/requirements.txt b/requirements.txt
index dbfe578..2359d77 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
 numpy
-scikit-learn
+scikit-learn==0.23.2
 pandas
 ipympl
\ No newline at end of file
diff --git a/setup.py b/setup.py
index a5c0cac..adf861d 100644
--- a/setup.py
+++ b/setup.py
@@ -30,7 +30,7 @@ setuptools.setup(
         "Topic :: Scientific/Engineering :: Artificial Intelligence",
         "Intended Audience :: Science/Research",
     ],
-    install_requires=["scikit-learn>=0.23.0", "numpy", "ipympl"],
+    install_requires=["scikit-learn==0.23.2", "numpy", "ipympl"],
     test_suite="stree.tests",
     zip_safe=False,
 )