diff --git a/lib/RandomLib/Generator.php b/lib/RandomLib/Generator.php
index 85e975c..8a19860 100644
--- a/lib/RandomLib/Generator.php
+++ b/lib/RandomLib/Generator.php
@@ -146,7 +146,7 @@ public function generateInt($min = 0, $max = PHP_INT_MAX) {
      * @return string The generated random string
      */
     public function generateString($length, $characters = '') {
-        if ($length == 0 || strlen($characters) == 1) {
+        if ($length == 0 || strlen($characters) == 0) {
             return '';
         } elseif (empty($characters)) {
             // Default to base 64