diff --git a/.github/workflows/debug.yml b/.github/workflows/debug.yml
index 8e32494..847ccbf 100644
--- a/.github/workflows/debug.yml
+++ b/.github/workflows/debug.yml
@@ -5,7 +5,7 @@ on:
         - debug
 jobs:
   debug:
-    runs-on: macos
+    runs-on: macos-10.15
     steps:
     - uses: actions/checkout@v2
     - uses: cachix/install-nix-action@v8