diff --git a/actions/attest_image/action.yaml b/actions/attest_image/action.yaml
index 07ed2977..2018562b 100644
--- a/actions/attest_image/action.yaml
+++ b/actions/attest_image/action.yaml
@@ -43,8 +43,8 @@ runs:
         SUBJECT_DIGEST: ${{ inputs.subject_digest }}
         IMAGE_REF: ${{ steps.ref.outputs.value }}
       run: |
-        # Accept either signer SAN: the reusable workflow under IABTechLab/uid2-shared-actions, or the caller's workflow via the composite path. --owner alone would reject the former (see https://github.com/cli/cli/issues/9045).
+        # Accept either signer SAN: the reusable workflow under IABTechLab/uid2-shared-actions, or the caller's workflow via the composite path. Certificate identities can differ in repository-name casing, so match them case-insensitively. --owner alone would reject the former (see https://github.com/cli/cli/issues/9045).
         gh attestation verify \
           "oci://${IMAGE_REF}@${SUBJECT_DIGEST}" \
           --owner "${{ github.repository_owner }}" \
-          --cert-identity-regex "^https://github\.com/(IABTechLab/uid2-shared-actions|${{ github.repository }})/"
+          --cert-identity-regex "(?i)^https://github\.com/(IABTechLab/uid2-shared-actions|${{ github.repository }})/"
diff --git a/actions/attest_image/tests/test_identity_regex.sh b/actions/attest_image/tests/test_identity_regex.sh
new file mode 100755
index 00000000..e72091c0
--- /dev/null
+++ b/actions/attest_image/tests/test_identity_regex.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# Tests the certificate identity policy embedded in ../action.yaml.
+set -euo pipefail
+
+action_file="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)/action.yaml"
+
+python3 - "$action_file" <<'PY'
+import re
+import sys
+from pathlib import Path
+
+action = Path(sys.argv[1]).read_text()
+match = re.search(r'--cert-identity-regex "([^"]+)"', action)
+if not match:
+    raise AssertionError("certificate identity regex not found in action.yaml")
+
+identity_regex = match.group(1).replace(
+    "${{ github.repository }}", "IABTechLab/uid2-examples"
+)
+policy = re.compile(identity_regex)
+
+accepted = [
+    "https://github.com/IABTechLab/uid2-shared-actions/.github/workflows/publish.yaml@refs/tags/v3",
+    "https://github.com/iabtechlab/uid2-shared-actions/.github/workflows/publish.yaml@refs/tags/v3",
+    "https://github.com/IABTechLab/uid2-examples/.github/workflows/release.yaml@refs/heads/main",
+    "https://github.com/iabtechlab/uid2-examples/.github/workflows/release.yaml@refs/heads/main",
+]
+rejected = [
+    "https://github.com/IABTechLab/uid2-shared-actions-malicious/.github/workflows/publish.yaml@refs/tags/v3",
+    "https://github.com/other-org/uid2-examples/.github/workflows/release.yaml@refs/heads/main",
+    "https://example.com/IABTechLab/uid2-shared-actions/.github/workflows/publish.yaml@refs/tags/v3",
+]
+
+for identity in accepted:
+    if not policy.match(identity):
+        raise AssertionError(f"expected identity to be accepted: {identity}")
+
+for identity in rejected:
+    if policy.match(identity):
+        raise AssertionError(f"expected identity to be rejected: {identity}")
+
+print("certificate identity regex tests passed")
+PY