diff --git a/release/cloudbuild-release.yaml b/release/cloudbuild-release.yaml
index 057462728..653140a32 100644
--- a/release/cloudbuild-release.yaml
+++ b/release/cloudbuild-release.yaml
@@ -288,11 +288,11 @@ steps:
   - |
     set -e
     # Check for a nomulus release tag (e.g., "v1.2.3")
-    if [[ "${TAG_NAME}" =~ ^nomulus-20\d{2}[0-1]\d[0-3]\d-RC\d{2}$ ]]; then
+    if [[ "${TAG_NAME}" =~ ^nomulus-20[0-9]{2}[0-1][0-9][0-3][0-9]-RC[0-9]{2}$ ]]; then
       echo "Tag format matches a nomulus release. Triggering nomulus build..."
       gcloud builds submit . --config=release/cloudbuild-nomulus.yaml --substitutions=TAG_NAME=$TAG_NAME
     # Check for a proxy release tag (e.g., "proxy-v1.2.3")
-    elif [[ "${TAG_NAME}" =~ ^proxy-20\d{2}[0-1]\d[0-3]\d-RC\d{2}$ ]]; then
+    elif [[ "${TAG_NAME}" =~ ^proxy-20[0-9]{2}[0-1][0-9][0-3][0-9]-RC[0-9]{2}$ ]]; then
       echo "Tag format matches a proxy release. Triggering proxy build..."
       gcloud builds submit . --config=release/cloudbuild-proxy.yaml --substitutions=TAG_NAME=$TAG_NAME
     else