diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8b1ca8d..caa7a17 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -46,7 +46,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [ubuntu-latest, macos-10.15, windows-latest]
         python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11-dev", "pypy-3.6", "pypy-3.7", "pypy-3.8"]
 
     name: Test