diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d77f429..eecda4e 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -19,6 +19,7 @@ jobs:
     outputs:
       should_build: ${{ steps.check_commit.outputs.should_build }}
       commit: ${{ steps.latest_commit.outputs.commit }}
+      commit_3_4_asan: ${{ steps.latest_commit_3_4_asan.outputs.commit }}
       previous_release: ${{ steps.check_commit.outputs.previous_release }}
       build_matrix: ${{ steps.matrix.outputs.build_matrix }}
       reuse_matrix: ${{ steps.matrix.outputs.reuse_matrix }}
@@ -32,19 +33,28 @@ jobs:
       id: latest_commit
       working-directory: ruby
       run: echo "commit=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
-
+    - name: Set latest commit (3.4-asan)
+      id: latest_commit_3_4_asan
+      working-directory: ruby
+      run: |
+        git fetch origin --depth=1 --no-tags '+refs/tags/v3_4_*:refs/tags/v3_4_*'
+        LATEST_TAG=$(git tag --list | grep -E "v3_4_[0-9]+$" | sort -V | tail -n1)
+        git checkout "$LATEST_TAG"
+        echo "commit=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
     - name: Check if latest commit already built
       uses: actions/github-script@v7
       id: check_commit
       with:
         script: |
           const latestDevCommit = "${{ steps.latest_commit.outputs.commit }}"
+          const latest34ASan = "${{ steps.latest_commit_3_4_asan.outputs.commit }}"
           const { owner, repo } = context.repo
           let { data: release } = await github.rest.repos.getLatestRelease({ owner, repo })
           const firstLine = release.body.split('\n')[0]
           const latestReleaseCommit = firstLine.split('@')[1]
           console.log(`Latest release commit: ${latestReleaseCommit}`)
           console.log(`Latest ruby commit: ${latestDevCommit}`)
+          console.log(`Latest 3.4-asan: ${latest34ASan}`)
           core.setOutput('should_build', latestReleaseCommit !== latestDevCommit)
           core.setOutput('previous_release', release.tag_name)
     - name: Compute build and reuse matrix
@@ -56,14 +66,14 @@ jobs:
           const skipSlow = "${{ github.event_name == 'workflow_dispatch' && github.event.inputs.skip_slow == 'true' }}"
           const buildMatrix = JSON.stringify(
             skipSlow === 'false' ?
-              { os: osList, name: ['head', 'debug'], include: [{ os: 'ubuntu-24.04', name: 'asan' }] } :
+              { os: osList, name: ['head', 'debug'], include: [{ os: 'ubuntu-24.04', name: 'asan' }, { os: 'ubuntu-24.04', name: '3.4-asan' }] } :
               { os: osList, name: ['head'] }
           )
           core.setOutput('build_matrix', buildMatrix)
           const reuseMatrix = JSON.stringify(
             skipSlow === 'false' ?
               { os: ['ubuntu-latest'], name: ['noop'] } : // GitHub doesn't like having an empty matrix, skips jobs that depend on reuse-slow
-              { os: osList, name: ['debug'], include: [{ os: 'ubuntu-24.04', name: 'asan' }] }
+              { os: osList, name: ['debug'], include: [{ os: 'ubuntu-24.04', name: 'asan' }, { os: 'ubuntu-24.04', name: '3.4-asan' }] }
           )
           core.setOutput('reuse_matrix', reuseMatrix)
           console.log(`build_matrix: ${buildMatrix}, reuse_matrix: ${reuseMatrix}`)
@@ -115,7 +125,7 @@ jobs:
       uses: actions/checkout@v4
       with:
         repository: ruby/ruby
-        ref: ${{ needs.prepare.outputs.commit }}
+        ref: ${{ matrix.name != '3.4-asan' && needs.prepare.outputs.commit || needs.prepare.outputs.commit_3_4_asan }}
     - name: Clone ruby-dev-builder
       uses: actions/checkout@v4
       with:
@@ -191,7 +201,7 @@ jobs:
         # Make the test timeouts more generous too (ASAN is slower)
         echo "RUBY_TEST_TIMEOUT_SCALE=5" >> $GITHUB_ENV
         echo "SYNTAX_SUGGEST_TIMEOUT=600" >> $GITHUB_ENV
-      if: matrix.name == 'asan'
+      if: matrix.name == 'asan' || matrix.name == '3.4-asan'
 
     # Build
     - run: mkdir -p ~/.rubies