diff --git a/CRM/Core/Smarty.php b/CRM/Core/Smarty.php
index 5c0d1d884a7f..41a70205753a 100644
--- a/CRM/Core/Smarty.php
+++ b/CRM/Core/Smarty.php
@@ -301,16 +301,26 @@ public static function registerStringResource() {
   }
 
   /**
-   * @param $path
+   * Add template directory(s).
+   *
+   * @param string|array $template_dir directory(s) of template sources
+   * @param string $key (Smarty3+) of the array element to assign the template dir to
+   * @param bool $isConfig (Smarty3+) true for config_dir
+   *
+   * @return Smarty          current Smarty instance for chaining
    */
-  public function addTemplateDir($path) {
+  public function addTemplateDir($template_dir, $key = NULL, $isConfig = FALSE) {
+    if (method_exists('parent', 'addTemplateDir')) {
+      // More recent versions of Smarty have this method.
+      return parent::addTemplateDir($template_dir, $key, $isConfig);
+    }
     if (is_array($this->template_dir)) {
-      array_unshift($this->template_dir, $path);
+      array_unshift($this->template_dir, $template_dir);
     }
     else {
-      $this->template_dir = [$path, $this->template_dir];
+      $this->template_dir = [$template_dir, $this->template_dir];
     }
-
+    return $this;
   }
 
   /**