diff --git a/lib/Client.php b/lib/Client.php
index 9c70850..77eac12 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -448,7 +448,7 @@ private function getNetwork($n)
         return $nf;
     }
     
-    public function encrypt($data, $key, $cipher_type = "AES-256-ECB", $iv = "", $auth_data = null)
+    public function encrypt($data, $key, $cipher_type = "AES-256-ECB", $iv = NULL, $auth_data = null)
     {
         # encryption using AES-256-ECB, AES-256-CBC, AES-256-GCM
         # data is string, key is hex string
@@ -496,7 +496,7 @@ public function pinToAesKey($pin, $iterations = 2048, $salt = "", $hash_function
         return $enc_key_32;
     }   
     
-    public function decrypt($b64ciphertext, $key, $cipher_type = "AES-256-ECB", $iv = "", $auth_tag = NULL, $auth_data = NULL)
+    public function decrypt($b64ciphertext, $key, $cipher_type = "AES-256-ECB", $iv = NULL, $auth_tag = NULL, $auth_data = NULL)
     {
         # data must be in base64 string, $key is binary of hashed pincode