diff --git a/.github/workflows/csharp-test.yml b/.github/workflows/csharp-test.yml
index befeefe728c..fed8d441dd8 100644
--- a/.github/workflows/csharp-test.yml
+++ b/.github/workflows/csharp-test.yml
@@ -140,3 +140,6 @@ jobs:
           UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
           UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
           UNITY_SERIAL: ${{ secrets.UNITY_SERIAL }}
+        # Skip if this is an external contribution.
+        # The license secrets will be empty, so the step would fail anyway.
+        if: ${{ !github.event.pull_request.head.repo.fork }}