diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c69ab85c..6a68aab4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -5,6 +5,9 @@ on:
 jobs:
   x86_64-linux:
     runs-on: ubuntu-latest
+    # We want to run on external PRs, but not on our own internal PRs as they'll be run by the push
+    # to the branch.
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
     steps:
       - name: Checkout
         uses: actions/checkout@v2
@@ -27,6 +30,9 @@ jobs:
         run: cd webgpu && zig build test
   x86_64-windows:
     runs-on: windows-latest
+    # We want to run on external PRs, but not on our own internal PRs as they'll be run by the push
+    # to the branch.
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
     steps:
       - name: Checkout
         uses: actions/checkout@v2
@@ -56,6 +62,9 @@ jobs:
         run: cd webgpu && zig build test
   x86_64-macos:
     runs-on: macos-latest
+    # We want to run on external PRs, but not on our own internal PRs as they'll be run by the push
+    # to the branch.
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
     steps:
       - name: Checkout
         uses: actions/checkout@v2