diff --git a/.github/workflows/unittests.yml b/.github/workflows/unittests.yml
index c38701a8..0d56228b 100644
--- a/.github/workflows/unittests.yml
+++ b/.github/workflows/unittests.yml
@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.6', '3.7', '3.8', '3.9']
+        python-version: ['3.6', '3.7', '3.8', '3.9', 'pypy3']
 
     steps:
     - uses: actions/checkout@v2
diff --git a/setup.py b/setup.py
index 615818bb..3a46a9c5 100644
--- a/setup.py
+++ b/setup.py
@@ -68,7 +68,8 @@
     extras_require={
         "docs": ["sphinx", "sphinx_rtd_theme", "sphinxcontrib-contentui"],
         "test": TESTS_REQUIRE,
-        "contrib": ["flake8", "flake8-bugbear", "black"] + TESTS_REQUIRE,
+        "contrib": ["flake8", "flake8-bugbear", "black; implementation_name=='cpython'"]
+        + TESTS_REQUIRE,
     },
     tests_require=TESTS_REQUIRE,
     zip_safe=False,