diff --git a/libs/Smarty.class.php b/libs/Smarty.class.php
index b8a7c209..0bb2b3a6 100644
--- a/libs/Smarty.class.php
+++ b/libs/Smarty.class.php
@@ -289,14 +289,14 @@ class Smarty extends Smarty_Internal_TemplateBase
      *
      * @var string
      */
-    public $joined_template_dir = '';
+    public $_joined_template_dir = null;
 
     /**
      * joined config directory string used in cache keys
      *
      * @var string
      */
-    public $joined_config_dir = '';
+    public $_joined_config_dir = null;
 
     /**
      * default template handler
@@ -908,7 +908,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     public function setTemplateDir($template_dir, $isConfig = false)
     {
         $type = $isConfig ? 'config_dir' : 'template_dir';
-        $joined = 'joined_' . $type;
+        $joined = '_joined_' . $type;
         $this->{$type} = (array) $template_dir;
         $this->{$joined} = join(' # ', $this->{$type});
         $this->_cache[$type . '_new'] = true;
@@ -928,7 +928,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     public function addTemplateDir($template_dir, $key = null, $isConfig = false)
     {
         $type = $isConfig ? 'config_dir' : 'template_dir';
-        $joined = 'joined_' . $type;
+        $joined = '_joined_' . $type;
         if (!isset($this->_cache[$type])) {
             $this->{$type} = (array) $this->{$type};
             $this->{$joined} = join(' # ', $this->{$type});
@@ -952,7 +952,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     {
         $type = $isConfig ? 'config_dir' : 'template_dir';
         if (!isset($this->_cache[$type])) {
-            $joined = 'joined_' . $type;
+            $joined = '_joined_' . $type;
             $this->{$type} = (array) $this->{$type};
             $this->{$joined} = join(' # ', $this->{$type});
             $this->_cache[$type] = false;
diff --git a/libs/sysplugins/smarty_internal_template.php b/libs/sysplugins/smarty_internal_template.php
index fd1ffd40..47de4a7a 100644
--- a/libs/sysplugins/smarty_internal_template.php
+++ b/libs/sysplugins/smarty_internal_template.php
@@ -444,7 +444,7 @@ class Smarty_Internal_Template extends Smarty_Internal_TemplateBase
         if ($this->smarty->allow_ambiguous_resources) {
             $_templateId = Smarty_Resource::getUniqueTemplateName($this, $template_name) . "#{$cache_id}#{$compile_id}";
         } else {
-            $_templateId = $this->smarty->joined_template_dir . "#{$template_name}#{$cache_id}#{$compile_id}";
+            $_templateId = $this->smarty->_joined_template_dir . "#{$template_name}#{$cache_id}#{$compile_id}";
         }
         if (isset($_templateId[150])) {
             $_templateId = sha1($_templateId);
diff --git a/libs/sysplugins/smarty_resource.php b/libs/sysplugins/smarty_resource.php
index 39a45329..f11bb678 100644
--- a/libs/sysplugins/smarty_resource.php
+++ b/libs/sysplugins/smarty_resource.php
@@ -103,9 +103,15 @@ abstract class Smarty_Resource
     public function buildUniqueResourceName(Smarty $smarty, $resource_name, $isConfig = false)
     {
         if ($isConfig) {
-            return get_class($this) . '#' . $smarty->joined_config_dir . '#' . $resource_name;
+            if (!isset($smarty->_joined_config_dir)) {
+                $smarty->getTemplateDir(null, true);
+            }
+            return get_class($this) . '#' . $smarty->_joined_config_dir . '#' . $resource_name;
         } else {
-            return get_class($this) . '#' . $smarty->joined_template_dir . '#' . $resource_name;
+            if (!isset($smarty->_joined_template_dir)) {
+                $smarty->getTemplateDir();
+            }
+            return get_class($this) . '#' . $smarty->_joined_template_dir . '#' . $resource_name;
         }
     }