diff --git a/.github/workflows/danger.yml b/.github/workflows/danger.yml
index 437c5d77..ec98f76c 100644
--- a/.github/workflows/danger.yml
+++ b/.github/workflows/danger.yml
@@ -15,7 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
-          - 2.7
+          - "2.7"
     steps:
       - name: Checkout
         uses: actions/checkout@v2
diff --git a/.github/workflows/style.yml b/.github/workflows/style.yml
index 539b3576..a4653064 100644
--- a/.github/workflows/style.yml
+++ b/.github/workflows/style.yml
@@ -22,7 +22,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
-          - 2.7
+          - "2.7"
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
diff --git a/.github/workflows/supported.yml b/.github/workflows/supported.yml
index 11a1bfbe..74f8bcf7 100644
--- a/.github/workflows/supported.yml
+++ b/.github/workflows/supported.yml
@@ -24,9 +24,9 @@ jobs:
         ruby:
           - truffleruby-head
           - ruby-head
-          - 3.1
-          - 3.0
-          - 2.7
+          - "3.1"
+          - "3.0"
+          - "2.7"
     runs-on: ubuntu-latest
     continue-on-error: ${{ matrix.allow_failure || endsWith(matrix.ruby, 'head') }}
     steps:
diff --git a/.github/workflows/unsupported.yml b/.github/workflows/unsupported.yml
index 1ebe11c7..e4fbe968 100644
--- a/.github/workflows/unsupported.yml
+++ b/.github/workflows/unsupported.yml
@@ -22,8 +22,8 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
-          - 2.6
-          - 2.5
+          - "2.6"
+          - "2.5"
     runs-on: ubuntu-20.04
     continue-on-error: ${{ matrix.allow_failure || endsWith(matrix.ruby, 'head') }}
     steps: