diff --git a/src/class.StringBuilder.php b/src/class.StringBuilder.php
index 456f202..a59cbf8 100644
--- a/src/class.StringBuilder.php
+++ b/src/class.StringBuilder.php
@@ -115,7 +115,7 @@ class StringBuilder {
      * @return string Wert der Variablen als String.
      */
     public function getVar(string $key) : string {
-        return $this->vars[trim($key)];
+        return $this->vars[trim($key)] ?? "";
     }
 
     /**