diff --git a/entrypoint.sh b/entrypoint.sh
index f04b921..7396119 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -6,7 +6,7 @@ set -a
 set +a
 
 REGISTRY="${IMAGEAPP%%/*}"
-export K8S_NS; K8S_NS="$(tr '[:upper:]' '[:lower:]' <<< "${GITHUB_REPOSITORY#*/}-$GITHUB_REF_NAME" | tr -c '[:lower:]-' -)"
+export K8S_NS; K8S_NS="$(printf '%s' "${GITHUB_REPOSITORY#*/}-$GITHUB_REF_NAME" | tr '[:upper:]' '[:lower:]' | tr -c '[:lower:][:digit:]-' - | sed 's/-\+/-/g; s/^-\+//; s/-$//')"
 
 mkdir -p "$HOME/.kube/"
 echo "$INPUT_KUBECONFIG" > "$HOME/.kube/config"