diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 67670b46c..e1bc703a7 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -15,7 +15,7 @@ on:
 jobs:
   build:
     name: CI build
-    runs-on: macos-11.0
+    runs-on: macos-10.15
     steps:
       - name: checkout
         uses: actions/checkout@v2