diff --git a/.github/workflows/swift.yml b/.github/workflows/swift.yml
index cd7e9378..e7c64f25 100644
--- a/.github/workflows/swift.yml
+++ b/.github/workflows/swift.yml
@@ -3,8 +3,6 @@ name: Swift
 on:
   push:
     branches: [ main ]
-  pull_request:
-    branches: [ main ]
   pull_request_target:
     branches: [ main ]
 
@@ -16,6 +14,8 @@ jobs:
       with:
         xcode-version: '13.0'
     - uses: actions/checkout@v2
+      with:
+        ref: ${{ github.event.pull_request.head.sha }}
     - uses: webfactory/ssh-agent@v0.5.3
       with:
         ssh-private-key: ${{ secrets.SOVRAN_SSH_KEY }}
@@ -31,6 +31,8 @@ jobs:
       with:
         swift-version: "5.4"
     - uses: actions/checkout@v2
+      with:
+        ref: ${{ github.event.pull_request.head.sha }}
     - uses: webfactory/ssh-agent@v0.5.3
       with:
         ssh-private-key: ${{ secrets.SOVRAN_SSH_KEY }}
@@ -46,6 +48,8 @@ jobs:
       with:
         xcode-version: '13.0'
     - uses: actions/checkout@v2
+      with:
+        ref: ${{ github.event.pull_request.head.sha }}
     - uses: webfactory/ssh-agent@v0.5.3
       with:
         ssh-private-key: ${{ secrets.SOVRAN_SSH_KEY }}
@@ -58,6 +62,8 @@ jobs:
       with:
         xcode-version: '13.0'
     - uses: actions/checkout@v2
+      with:
+        ref: ${{ github.event.pull_request.head.sha }}
     - uses: webfactory/ssh-agent@v0.5.3
       with:
         ssh-private-key: ${{ secrets.SOVRAN_SSH_KEY }}
@@ -70,6 +76,8 @@ jobs:
       with:
         xcode-version: '13.0'
     - uses: actions/checkout@v2
+      with:
+        ref: ${{ github.event.pull_request.head.sha }}
     - uses: webfactory/ssh-agent@v0.5.3
       with:
         ssh-private-key: ${{ secrets.SOVRAN_SSH_KEY }}
@@ -82,6 +90,8 @@ jobs:
       with:
         xcode-version: '13.0'
     - uses: actions/checkout@v2
+      with:
+        ref: ${{ github.event.pull_request.head.sha }}
     - uses: webfactory/ssh-agent@v0.5.3
       with:
         ssh-private-key: ${{ secrets.SOVRAN_SSH_KEY }}