diff --git a/.duplicate-id-guard b/.duplicate-id-guard
new file mode 100644
index 0000000..c4d6447
--- /dev/null
+++ b/.duplicate-id-guard
@@ -0,0 +1,3 @@
+This file causes merge conflicts if two ID assignment jobs run concurrently.
+This prevents duplicate ID assignment due to a race between those jobs.
+90b4c5be517867a32fc05e59aac80a51dff30a8961ac5261357d06dfb1b892fd  -
diff --git a/.github/workflows/assign-ids.yml b/.github/workflows/assign-ids.yml
index 63c37a3..7ddf274 100644
--- a/.github/workflows/assign-ids.yml
+++ b/.github/workflows/assign-ids.yml
@@ -29,6 +29,12 @@ jobs:
         message=$(rustsec-admin assign-id --github-actions-output)
         echo "::set-output name=commit_message::${message}"
 
+    - name: Create duplicate ID assignment guard
+      run: |
+        echo "This file causes merge conflicts if two ID assignment jobs run concurrently." > .duplicate-id-guard
+        echo "This prevents duplicate ID assignment due to a race between those jobs." >> .duplicate-id-guard
+        ls -R . | sha256sum >> .duplicate-id-guard
+
     - name: Lint advisories
       run: rustsec-admin lint