diff --git a/.github/workflows/cache-merge.yml b/.github/workflows/cache-merge.yml
index ee7a5f9..b6e84b6 100644
--- a/.github/workflows/cache-merge.yml
+++ b/.github/workflows/cache-merge.yml
@@ -20,7 +20,8 @@ jobs:
     name: Merge similar caches
     strategy:
       matrix:
-        os: [ubuntu-latest]
+        os:
+          - [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout this repo
@@ -69,7 +70,8 @@ jobs:
     needs: merge-similar-caches
     strategy:
       matrix:
-        os: [ubuntu-latest]
+        os:
+          - [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout this repo