diff --git a/library/HTMLPurifier/URISchemeRegistry.php b/library/HTMLPurifier/URISchemeRegistry.php
index 6adaf155..576bf7b6 100644
--- a/library/HTMLPurifier/URISchemeRegistry.php
+++ b/library/HTMLPurifier/URISchemeRegistry.php
@@ -36,21 +36,20 @@ class HTMLPurifier_URISchemeRegistry
      */
     public function getScheme($scheme, $config, $context) {
         if (!$config) $config = HTMLPurifier_Config::createDefault();
-        $null = null; // for the sake of passing by reference
 
         // important, otherwise attacker could include arbitrary file
         $allowed_schemes = $config->get('URI.AllowedSchemes');
         if (!$config->get('URI.OverrideAllowedSchemes') &&
             !isset($allowed_schemes[$scheme])
         ) {
-            return $null;
+            return;
         }
 
         if (isset($this->schemes[$scheme])) return $this->schemes[$scheme];
-        if (!isset($allowed_schemes[$scheme])) return $null;
+        if (!isset($allowed_schemes[$scheme])) return;
 
         $class = 'HTMLPurifier_URIScheme_' . $scheme;
-        if (!class_exists($class)) return $null;
+        if (!class_exists($class)) return;
         $this->schemes[$scheme] = new $class();
         return $this->schemes[$scheme];
     }