diff --git a/tests/MCryptCompatTest.php b/tests/MCryptCompatTest.php
index cb7534e..f52a6ba 100644
--- a/tests/MCryptCompatTest.php
+++ b/tests/MCryptCompatTest.php
@@ -860,7 +860,7 @@ public function testOldMcryptShortIV()
 
     public function testOldMcryptNoIV()
     {
-        $key = str_pad($key, $length, "\0");
+        $key = str_pad('key', $length, "\0");
         $data = 'data';
         $iv = null;