diff --git a/includes/classes/class.issuupanelconfig.php b/includes/classes/class.issuupanelconfig.php
index bd43237..8741f1e 100644
--- a/includes/classes/class.issuupanelconfig.php
+++ b/includes/classes/class.issuupanelconfig.php
@@ -3,11 +3,11 @@
 class IssuuPanelConfig
 {
 
-	private $issuuPanelDebug;
+    private $issuuPanelDebug;
 
     private $mobileDetect;
 
-	private $issuuPanelCatcher;
+    private $issuuPanelCatcher;
 
     private $issuuPanelSimpleReader;
 
@@ -107,7 +107,7 @@ public function __construct(
         $this->issuuPanelCacheManager = new IssuuPanelCacheManager($this->getOptionEntity());
 
         // IssuuServiceApi
-        if (!empty($this->getOptionEntity()->getApiKey()) && !empty($this->getOptionEntity()->getApiSecret()))
+        if (!strlen($this->getOptionEntity()->getApiKey()) > 0 && !strlen($this->getOptionEntity()->getApiSecret()) > 0)
         {
             $this->issuuServiceApi = array(
                 'IssuuDocument' => new IssuuDocument(
diff --git a/issuu-panel.php b/issuu-panel.php
index 4ab5cd1..65af393 100644
--- a/issuu-panel.php
+++ b/issuu-panel.php
@@ -3,7 +3,7 @@
 Plugin Name: Issuu Panel
 Plugin URI: https://github.com/Issuu-Panel-WordPress-Plugin/issuu-panel
 Description: Admin panel for Issuu. You can upload your documents, create folders and embed documents in posts.
-Version: 1.6.3
+Version: 1.6.4
 Author: Pedro Marcelo
 Author URI: https://www.linkedin.com/profile/view?id=265534858
 License: GPL3
@@ -11,7 +11,7 @@
 
 if (defined('ISSUU_PANEL_VERSION'))
 {
-	switch (version_compare(ISSUU_PANEL_VERSION, '1.6.3')) {
+	switch (version_compare(ISSUU_PANEL_VERSION, '1.6.4')) {
 		case -1:
 			wp_die("A lower version of Issuu Panel plugin is already installed");
 			break;
@@ -30,7 +30,7 @@
 |--------------------------------------
 */
 
-define('ISSUU_PANEL_VERSION', '1.6.3');
+define('ISSUU_PANEL_VERSION', '1.6.4');
 define('ISSUU_PANEL_DIR', plugin_dir_path(__FILE__));
 define('ISSUU_PANEL_URL', plugin_dir_url(__FILE__));
 define('ISSUU_PANEL_PREFIX', 'issuu_painel_');
diff --git a/readme.txt b/readme.txt
index 44c9469..543b9a9 100644
--- a/readme.txt
+++ b/readme.txt
@@ -105,6 +105,9 @@ You can send the translation by e-mail. Send for pedromarcelodesaalves@gmail.com
 
 == Changelog ==
 
+= 1.6.4 =
+* Fixed: Check API key and API secret values with strlen function
+
 = 1.6.3 =
 * Updated: Plugin structure is event-based now
 * Fixed: Upload documents on PHP 5.5 version or upper