diff --git a/debian/debian-secure.sh b/debian/debian-secure.sh
index 3073fe8..653bc9e 100644
--- a/debian/debian-secure.sh
+++ b/debian/debian-secure.sh
@@ -12,14 +12,14 @@ useradd -m -s /bin/bash $USERNAME
 
 echo "Configuring WireGuard..."
 
-if [ -z "$CLIENT_IP" ] || [ -z "$SERVER_IP" ] || [ -z "$PREFIXLEN" ]; then
+if [[ -z "$CLIENT_IP" ]] || [[ -z "$SERVER_IP" ]] || [[ -z "$PREFIXLEN" ]]; then
   SUB_START="fc$(openssl rand -hex 1):$(openssl rand -hex 2):$(openssl rand -hex 2):$(openssl rand -hex 2)"
   CLIENT_IP="$SUB_START::2"
   SERVER_IP="$SUB_START::1"
   PREFIXLEN=64
 fi
 
-if [ "$CLIENT_IP" == *"."* ]; then
+if [[ "$CLIENT_IP" == *"."* ]]; then
   HOST_MASK=32
 else
   HOST_MASK=128