diff --git a/.github/workflows/differential-shellcheck.yml b/.github/workflows/differential-shellcheck.yml
new file mode 100644
index 0000000..20913cc
--- /dev/null
+++ b/.github/workflows/differential-shellcheck.yml
@@ -0,0 +1,28 @@
+name: Differential ShellCheck
+on:
+  push:
+    branches: [ trunk ]
+  pull_request:
+    branches: [ trunk ]
+
+permissions:
+  contents: read
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    permissions:
+      security-events: write
+
+    steps:
+      - name: Repository checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - id: ShellCheck
+        name: Differential ShellCheck
+        uses: redhat-plumbers-in-action/differential-shellcheck@v5
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/build_and_release.sh b/build_and_release.sh
index e4c9cf6..3f2f171 100755
--- a/build_and_release.sh
+++ b/build_and_release.sh
@@ -24,7 +24,7 @@ if [[ $GH_RELEASE_TAG = *-* ]]; then
 fi
 
 draft_release=""
-if [[ "$DRAFT_RELEASE" = "true" ]]; then
+if [[ "${DRAFT_RELEASE:-}" = "true" ]]; then
   draft_release="--draft"
 fi