diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 978ae766..1aca7e79 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -24,7 +24,7 @@ jobs:
         with:
           node-version: 16.x
       - name: Install dependencies
-        run: yarn install --check-files --frozen-lockfile
+        run: yarn install --check-files
       - name: build
         run: npx projen build
       - name: Find mutations
@@ -52,6 +52,37 @@ jobs:
         with:
           name: build-artifact
           path: dist
+  self-mutation:
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    if: always() && needs.build.outputs.self_mutation_happened && !(github.event.pull_request.head.repo.full_name != github.repository)
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          token: ${{ secrets.PROJEN_GITHUB_TOKEN }}
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+      - name: Download patch
+        uses: actions/download-artifact@v3
+        with:
+          name: .repo.patch
+          path: ${{ runner.temp }}
+      - name: Apply patch
+        run: '[ -s ${{ runner.temp }}/.repo.patch ] && git apply ${{ runner.temp }}/.repo.patch || echo "Empty patch. Skipping."'
+      - name: Set git identity
+        run: |-
+          git config user.name "github-actions"
+          git config user.email "github-actions@github.com"
+      - name: Push changes
+        env:
+          PULL_REQUEST_REF: ${{ github.event.pull_request.head.ref }}
+        run: |-
+          git add .
+          git commit -s -m "chore: self mutation"
+          git push origin HEAD:$PULL_REQUEST_REF
   package-js:
     needs: build
     runs-on: ubuntu-latest
diff --git a/.projenrc.ts b/.projenrc.ts
index 47c51be2..8e203580 100644
--- a/.projenrc.ts
+++ b/.projenrc.ts
@@ -41,6 +41,5 @@ const project = new awscdk.AwsCdkConstructLibrary({
   copyrightPeriod: '2023-',
   copyrightOwner: 'Amazon.com, Inc. or its affiliates. All Rights Reserved.',
   gitignore: ['*.DS_STORE'],
-  mutableBuild: false,
 });
 project.synth();