diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 01eefbfec4..10b4b2b832 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -160,14 +160,15 @@ jobs:
   benchmark:
     name: Run benchmark
     runs-on: ubuntu-latest
-    env:
-      COMMITS_TO_TEST: ${{ github.event.pull_request.commits || 1 }}
+    if: github.event_name == 'pull_request'
     steps:
       - name: Checkout repo
         uses: actions/checkout@v2
 
       - name: Deepen cloned repo
-        run: 'git fetch --deepen=$COMMITS_TO_TEST'
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        run: 'git fetch --depth=1 origin $BASE_SHA:refs/tags/BASE'
 
       - name: Setup Node.js
         uses: actions/setup-node@v2
@@ -179,19 +180,20 @@ jobs:
         run: npm ci --ignore-scripts
 
       - name: Run Benchmark
-        run: 'npm run benchmark -- --revs HEAD "HEAD~$COMMITS_TO_TEST"'
+        run: 'npm run benchmark -- --revs HEAD BASE'
 
   diff-npm-package:
     name: Diff content of NPM package
     runs-on: ubuntu-latest
-    env:
-      COMMITS_TO_TEST: ${{ github.event.pull_request.commits || 1 }}
+    if: github.event_name == 'pull_request'
     steps:
       - name: Checkout repo
         uses: actions/checkout@v2
 
       - name: Deepen cloned repo
-        run: 'git fetch --deepen=$COMMITS_TO_TEST'
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        run: 'git fetch --depth=1 origin $BASE_SHA:refs/tags/BASE'
 
       - name: Setup Node.js
         uses: actions/setup-node@v2
@@ -203,7 +205,7 @@ jobs:
         run: npm ci --ignore-scripts
 
       - name: Generate report
-        run: 'node resources/diff-npm-package.js HEAD~$COMMITS_TO_TEST HEAD'
+        run: 'node resources/diff-npm-package.js BASE HEAD'
 
       - name: Upload generated report
         uses: actions/upload-artifact@v2