diff --git a/src/Encryption/Encryptor.php b/src/Encryption/Encryptor.php
index fa6c2b724..d8da47224 100644
--- a/src/Encryption/Encryptor.php
+++ b/src/Encryption/Encryptor.php
@@ -210,10 +210,14 @@ public function decode($decrypted)
      */
     protected function getAESKey()
     {
-        if (empty($this->AESKey) || strlen($this->AESKey) !== 43) {
+        if (empty($this->AESKey)) {
             throw new InvalidConfigException("Configuration mission, 'aes_key' is required.");
         }
 
+        if (strlen($this->AESKey) !== 43) {
+            throw new InvalidConfigException("The length of 'aes_key' must be 43.");
+        }
+
         return base64_decode($this->AESKey.'=', true);
     }