diff --git a/.github/workflows/mt.yml b/.github/workflows/mt.yml
index 02da861..a9a165e 100644
--- a/.github/workflows/mt.yml
+++ b/.github/workflows/mt.yml
@@ -54,4 +54,5 @@ jobs:
       - name: Run Infection
         if: github.event_name == 'pull_request'
         run: |
-          vendor/bin/infection --coverage=build/logs --threads=$(nproc) --show-mutations --no-interaction --only-covered --only-covering-test-cases --skip-initial-tests
+          git fetch --depth=1 origin $GITHUB_BASE_REF
+          vendor/bin/infection --coverage=build/logs --threads=$(nproc) --show-mutations --no-interaction --only-covered --only-covering-test-cases --skip-initial-tests --git-diff-lines --git-diff-base=origin/$GITHUB_BASE_REF