diff --git a/tst/serversalt.php b/tst/serversalt.php
index d11454f..9756455 100644
--- a/tst/serversalt.php
+++ b/tst/serversalt.php
@@ -37,21 +37,24 @@ class serversaltTest extends PHPUnit_Framework_TestCase
         $salt = serversalt::get();
 
         // mcrypt mock
-        if (!defined('MCRYPT_DEV_URANDOM')) define('MCRYPT_DEV_URANDOM', 1);
-        function mcrypt_create_iv($int, $flag)
+        if (!function_exists('mcrypt_create_iv'))
         {
-            $randomSalt = '';
-            for($i = 0; $i < 256; ++$i) {
-                $randomSalt .= base_convert(mt_rand(), 10, 16);
-            }
-            // hex2bin requires an even length, pad if necessary
-            if (strlen($randomSalt) % 2)
+            if (!defined('MCRYPT_DEV_URANDOM')) define('MCRYPT_DEV_URANDOM', 1);
+            function mcrypt_create_iv($int, $flag)
             {
-                $randomSalt = '0' . $randomSalt;
+                $randomSalt = '';
+                for($i = 0; $i < 256; ++$i) {
+                    $randomSalt .= base_convert(mt_rand(), 10, 16);
+                }
+                // hex2bin requires an even length, pad if necessary
+                if (strlen($randomSalt) % 2)
+                {
+                    $randomSalt = '0' . $randomSalt;
+                }
+                return hex2bin($randomSalt);
             }
-            return hex2bin($randomSalt);
+            $this->assertNotEquals($salt, serversalt::generate());
         }
-        $this->assertNotEquals($salt, serversalt::generate());
 
         // try setting a different path and resetting it
         serversalt::setPath($this->_otherPath);