diff --git a/.github/actions/setup/mmtkbuilder/action.yml b/.github/actions/setup/mmtkbuilder/action.yml
deleted file mode 100644
index c9acfd9..0000000
--- a/.github/actions/setup/mmtkbuilder/action.yml
+++ /dev/null
@@ -1,60 +0,0 @@
-name: MMTk Builder
-description: >-
-  Installs and configures OS Ruby build deps and Rust for MMTk
-
-inputs:
-  os:
-    desciption: Short string representing OS (ubuntu|macos)
-    required: true
-    default: ubuntu
-
-  mmtk_plan:
-    description: the MMTk plan name to store in the environment
-    require: true
-    default: MarkSweep
-
-  mmtk_build:
-    description: The MMTk build (debug|release)
-    require: true
-    default: release
-
-runs:
-  using: composite
-  steps:
-    - name: Install libraries (macOS)
-      shell: bash
-      uses: ./.github/actions/setup/macos
-      if: ${{ contains(inputs.os, 'macos') }}
-
-    - name: Install libraries (Ubuntu)
-      shell: bash
-      uses: ./.github/actions/setup/ubuntu
-      if: ${{ contains(inputs.os, 'ubuntu') }}
-
-    - uses: actions-rust-lang/setup-rust-toolchain@v1
-    - name: Set MMTk environment variables
-      shell: bash
-      run: |
-        if [[ ${{ inputs.mmtk_build }} == debug ]]; then
-          echo 'RUST_LOG=' >> $GITHUB_ENV
-          # Debug builds run much slower so we should increase the timeout
-          echo 'RUBY_TEST_TIMEOUT_SCALE=10' >> $GITHUB_ENV
-          # SYNTAX_SUGGEST_TIMEOUT defaults to 1 second
-          echo 'SYNTAX_SUGGEST_TIMEOUT=60' >> $GITHUB_ENV
-        fi
-        echo 'MMTK_PLAN=${{ inputs.mmtk_plan }}' >> $GITHUB_ENV
-
-    - uses: ruby/setup-ruby@a6e6f86333f0a2523ece813039b8b4be04560854 # v1.190.0
-      shell: bash
-      with:
-        ruby-version: '3.3'
-      if: ${{ contains(inputs.os, 'ubuntu') }}
-
-    - name: make sure that kern.coredump=1
-      shell: bash
-      run: |
-        sysctl -n kern.coredump
-        sudo sysctl -w kern.coredump=1
-        sudo chmod -R +rwx /cores/
-      if: ${{ contains(inputs.os, 'macos') }}
-
diff --git a/.github/workflows/mmtk-builder.yml b/.github/workflows/mmtk-builder.yml
new file mode 100644
index 0000000..c65db3e
--- /dev/null
+++ b/.github/workflows/mmtk-builder.yml
@@ -0,0 +1,62 @@
+name: MMTk Builder
+description: >-
+  Installs and configures OS Ruby build deps and Rust for MMTk
+
+on:
+  workflow_call:
+    inputs:
+      os:
+        desciption: Short string representing OS (ubuntu|macos)
+        required: true
+        default: ubuntu
+
+      mmtk_plan:
+        description: the MMTk plan name to store in the environment
+        require: true
+        default: MarkSweep
+
+      mmtk_build:
+        description: The MMTk build (debug|release)
+        require: true
+        default: release
+
+jobs:
+  build:
+    steps:
+      - name: Install libraries (macOS)
+        shell: bash
+        uses: ./.github/actions/setup/macos
+        if: ${{ contains(inputs.os, 'macos') }}
+
+      - name: Install libraries (Ubuntu)
+        shell: bash
+        uses: ./.github/actions/setup/ubuntu
+        if: ${{ contains(inputs.os, 'ubuntu') }}
+
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - name: Set MMTk environment variables
+        shell: bash
+        run: |
+          if [[ ${{ inputs.mmtk_build }} == debug ]]; then
+            echo 'RUST_LOG=' >> $GITHUB_ENV
+            # Debug builds run much slower so we should increase the timeout
+            echo 'RUBY_TEST_TIMEOUT_SCALE=10' >> $GITHUB_ENV
+            # SYNTAX_SUGGEST_TIMEOUT defaults to 1 second
+            echo 'SYNTAX_SUGGEST_TIMEOUT=60' >> $GITHUB_ENV
+          fi
+          echo 'MMTK_PLAN=${{ inputs.mmtk_plan }}' >> $GITHUB_ENV
+
+      - uses: ruby/setup-ruby@a6e6f86333f0a2523ece813039b8b4be04560854 # v1.190.0
+        shell: bash
+        with:
+          ruby-version: '3.3'
+        if: ${{ contains(inputs.os, 'ubuntu') }}
+
+      - name: make sure that kern.coredump=1
+        shell: bash
+        run: |
+          sysctl -n kern.coredump
+          sudo sysctl -w kern.coredump=1
+          sudo chmod -R +rwx /cores/
+        if: ${{ contains(inputs.os, 'macos') }}
+
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 7a2ece1..ffde23f 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -32,14 +32,16 @@ jobs:
 
     runs-on: ${{ matrix.os }}
 
+    build:
+      uses: ./.github/workflows/mmtk-builder.yml
+      with:
+        os: ${{ matrix.os }}
+        mmtk_plan: ${{ matrix.gc.mmtk_plan }}
+        mmtk_build: ${{ matrix.gc.mmtk_build }}
+
+
     steps:
       - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
-      - uses: ./.github/actions/setup/mmtkbuilder
-        with:
-          os: ${{ matrix.os }}
-          mmtk_plan: ${{ matrix.gc.mmtk_plan }}
-          mmtk_build: ${{ matrix.gc.mmtk_build }}
-
       - name: Install Bundler dependencies
         run: bundle install