diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d45cfead1..92e77ac2c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -41,6 +41,11 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6
+      - name: "Test Ruby 4.0"
+        uses: ./.github/actions/test_gem
+        with:
+          gem: "${{ matrix.gem }}"
+          ruby: "4.0"
       - name: "Test Ruby 3.4"
         uses: ./.github/actions/test_gem
         with:
@@ -108,6 +113,11 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6
+      - name: "Test Ruby 4.0"
+        uses: ./.github/actions/test_gem
+        with:
+          gem: "${{ matrix.gem }}"
+          ruby: "4.0"
       - name: "Test Ruby 3.4"
         if: "${{ matrix.gem != 'opentelemetry-exporter-jaeger' }}"
         uses: ./.github/actions/test_gem
@@ -178,6 +188,11 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6
+      - name: "Test Ruby 4.0"
+        uses: ./.github/actions/test_gem
+        with:
+          gem: "${{ matrix.gem }}"
+          ruby: "4.0"
       - name: "Test Ruby 3.4"
         uses: ./.github/actions/test_gem
         with:
diff --git a/.github/workflows/fossa.yml b/.github/workflows/fossa.yml
index e465c635d..5a1f47990 100644
--- a/.github/workflows/fossa.yml
+++ b/.github/workflows/fossa.yml
@@ -15,10 +15,10 @@ jobs:
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
 
-      - name: Install Ruby 3.4
+      - name: Install Ruby
         uses: ruby/setup-ruby@b90be12699fdfcbee4440c2bba85f6f460446bb0 # v1.279.0
         with:
-          ruby-version: 3.4
+          ruby-version: 4.0
       - name: Generate Gemfile.lock
         run: |
           echo "Finding all Gemfiles in the project..."