diff --git a/.github/workflows/github-release.yml b/.github/workflows/github-release.yml
index f4ae4da2..1982507d 100644
--- a/.github/workflows/github-release.yml
+++ b/.github/workflows/github-release.yml
@@ -84,10 +84,9 @@ jobs:
             exit 1
           fi
 
-      - name: Check out trusted main history
+      - name: Check out trusted base history
         uses: actions/checkout@v4
         with:
-          ref: main
           fetch-depth: 0
           persist-credentials: false
 
@@ -96,9 +95,11 @@ jobs:
           TARGET_SHA: ${{ steps.release.outputs.target_sha }}
         run: |
           set -euo pipefail
-          git fetch --no-tags origin refs/heads/main:refs/remotes/origin/main
+          git fetch --no-tags origin main
           git cat-file -e "$TARGET_SHA^{commit}"
-          git merge-base --is-ancestor "$TARGET_SHA" refs/remotes/origin/main
+          git merge-base --is-ancestor "$TARGET_SHA" origin/main
+          git checkout --detach "$TARGET_SHA"
+          test "$(git rev-parse HEAD)" = "$TARGET_SHA"
 
       - name: Download and verify OSS artifacts
         env:
diff --git a/tests/release-workflow.test.ts b/tests/release-workflow.test.ts
index a43d698a..1a58a965 100644
--- a/tests/release-workflow.test.ts
+++ b/tests/release-workflow.test.ts
@@ -54,24 +54,28 @@ describe("GitHub release workflow", () => {
   });
 
   it("keeps merged fork code out of the trusted release checkout", () => {
-    const checkout = steps.find((step) => step.name === "Check out trusted main history");
+    const checkout = steps.find((step) => step.name === "Check out trusted base history");
     expect(checkout?.uses).toBe("actions/checkout@v4");
-    expect(checkout?.with).toEqual(
-      expect.objectContaining({
-        ref: "main",
-        "fetch-depth": 0,
-        "persist-credentials": false,
-      }),
-    );
-    expect(JSON.stringify(checkout?.with)).not.toContain("target_sha");
+    expect(checkout?.with).toEqual({
+      "fetch-depth": 0,
+      "persist-credentials": false,
+    });
+    expect(checkout?.with).not.toHaveProperty("ref");
+    expect(JSON.stringify(checkout)).not.toContain("github.event.pull_request");
+    expect(source).not.toContain("refs/pull/");
     expect(source).not.toContain("allow-unsafe-pr-checkout");
 
     const verifyScript = script("Verify target is on main");
-    expect(verifyScript).toContain("refs/heads/main:refs/remotes/origin/main");
+    expect(verifyScript).toContain("git fetch --no-tags origin main");
     expect(verifyScript).toContain('git cat-file -e "$TARGET_SHA^{commit}"');
-    expect(verifyScript).toContain(
-      'git merge-base --is-ancestor "$TARGET_SHA" refs/remotes/origin/main',
-    );
+    const ancestorCheck = 'git merge-base --is-ancestor "$TARGET_SHA" origin/main';
+    const detachTarget = 'git checkout --detach "$TARGET_SHA"';
+    const verifyHead = 'test "$(git rev-parse HEAD)" = "$TARGET_SHA"';
+    expect(verifyScript).toContain(ancestorCheck);
+    expect(verifyScript).toContain(detachTarget);
+    expect(verifyScript).toContain(verifyHead);
+    expect(verifyScript.indexOf(detachTarget)).toBeGreaterThan(verifyScript.indexOf(ancestorCheck));
+    expect(verifyScript.indexOf(verifyHead)).toBeGreaterThan(verifyScript.indexOf(detachTarget));
 
     const notesScript = script("Build release notes");
     expect(notesScript).toContain('manual_object="${TARGET_SHA}:${manual_notes}"');