diff --git a/.github/workflows/oxipng.yml b/.github/workflows/oxipng.yml
index 51f2ac6e..f1e335ae 100644
--- a/.github/workflows/oxipng.yml
+++ b/.github/workflows/oxipng.yml
@@ -15,6 +15,9 @@ jobs:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
 
+    # Prevent in-repo PRs from running the same jobs twice
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.fork
+
     strategy:
       fail-fast: false
       matrix:
@@ -151,6 +154,9 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
 
+    # Prevent in-repo PRs from running the same jobs twice
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.fork
+
     steps:
       - name: Checkout source
         uses: actions/checkout@v3