diff --git a/library/HTMLPurifier/AttrDef/URI.php b/library/HTMLPurifier/AttrDef/URI.php
index 1f5cd816..850e953b 100644
--- a/library/HTMLPurifier/AttrDef/URI.php
+++ b/library/HTMLPurifier/AttrDef/URI.php
@@ -46,10 +46,10 @@ class HTMLPurifier_AttrDef_URI extends HTMLPurifier_AttrDef
             // no need to validate the scheme's fmt since we do that when we
             // retrieve the specific scheme object from the registry
             $scheme = ctype_lower($scheme) ? $scheme : strtolower($scheme);
-            $scheme_obj =& $registry->getScheme($scheme);
+            $scheme_obj =& $registry->getScheme($scheme, $config);
             if (!$scheme_obj) return ''; // invalid scheme, clean it out
         } else {
-            $scheme_obj =& $registry->getScheme($config->get('URI', 'DefaultScheme'));
+            $scheme_obj =& $registry->getScheme($config->get('URI', 'DefaultScheme'), $config);
         }
         
         
diff --git a/library/HTMLPurifier/URISchemeRegistry.php b/library/HTMLPurifier/URISchemeRegistry.php
index fb2540f9..f925d009 100644
--- a/library/HTMLPurifier/URISchemeRegistry.php
+++ b/library/HTMLPurifier/URISchemeRegistry.php
@@ -52,6 +52,10 @@ class HTMLPurifier_URISchemeRegistry
         return $this->schemes[$scheme];
     }
     
+    function register($scheme, &$scheme_obj) {
+        $this->schemes[$scheme] =& $scheme_obj;
+    }
+    
 }
 
-?>
\ No newline at end of file
+?>
diff --git a/tests/HTMLPurifier/AttrDef/URITest.php b/tests/HTMLPurifier/AttrDef/URITest.php
index 5b4d1a58..13c3153d 100644
--- a/tests/HTMLPurifier/AttrDef/URITest.php
+++ b/tests/HTMLPurifier/AttrDef/URITest.php
@@ -195,11 +195,11 @@ class HTMLPurifier_AttrDef_URITest extends HTMLPurifier_AttrDefHarness
         $this->scheme =& new HTMLPurifier_URISchemeMock($this);
         
         // here are the schemes we will support with overloaded mocks
-        $registry->setReturnReference('getScheme', $this->scheme, array('http'));
-        $registry->setReturnReference('getScheme', $this->scheme, array('mailto'));
+        $registry->setReturnReference('getScheme', $this->scheme, array('http', $this->config));
+        $registry->setReturnReference('getScheme', $this->scheme, array('mailto', $this->config));
         
         // default return value is false (meaning no scheme defined: reject)
-        $registry->setReturnValue('getScheme', false, array('*'));
+        $registry->setReturnValue('getScheme', false, array('*', $this->config));
         
         if ($this->components === false) {
             $this->scheme->expectNever('validateComponents');
diff --git a/tests/HTMLPurifier/AttrDefHarness.php b/tests/HTMLPurifier/AttrDefHarness.php
index 893877d6..8c130ef9 100644
--- a/tests/HTMLPurifier/AttrDefHarness.php
+++ b/tests/HTMLPurifier/AttrDefHarness.php
@@ -10,9 +10,9 @@ class HTMLPurifier_AttrDefHarness extends UnitTestCase
     // cannot be used for accumulator
     function assertDef($string, $expect = true, $message = '%s') {
         // $expect can be a string or bool
-        $this->setUpAssertDef();
         if (!$this->config) $this->config = HTMLPurifier_Config::createDefault();
         if (!$this->context) $this->context = new HTMLPurifier_AttrContext();
+        $this->setUpAssertDef();
         $result = $this->def->validate($string, $this->config, $this->context);
         if ($expect === true) {
             $this->assertIdentical($string, $result, $message);
diff --git a/tests/HTMLPurifier/URISchemeRegistryTest.php b/tests/HTMLPurifier/URISchemeRegistryTest.php
index 7b46b3bd..b736fd30 100644
--- a/tests/HTMLPurifier/URISchemeRegistryTest.php
+++ b/tests/HTMLPurifier/URISchemeRegistryTest.php
@@ -7,11 +7,32 @@ class HTMLPurifier_URISchemeRegistryTest extends UnitTestCase
     
     function test() {
         
-        $registry =& HTMLPurifier_URISchemeRegistry::instance();
+        generate_mock_once('HTMLPurifier_URIScheme');
+        
+        $config = HTMLPurifier_Config::createDefault();
+        $config->set('URI', 'AllowedSchemes', array('http' => true, 'telnet' => true));
+        
+        $registry = new HTMLPurifier_URISchemeRegistry();
         $this->assertIsA($registry->getScheme('http'), 'HTMLPurifier_URIScheme_http');
         
-        // to come: overloading and custom schemes, as well as changing the
-        // configuration values used by this class
+        $scheme_http = new HTMLPurifier_URISchemeMock($this);
+        $scheme_telnet = new HTMLPurifier_URISchemeMock($this);
+        $scheme_foobar = new HTMLPurifier_URISchemeMock($this);
+        
+        // register a new scheme
+        $registry->register('telnet', $scheme_telnet);
+        $this->assertIdentical($registry->getScheme('telnet', $config), $scheme_telnet);
+        
+        // overload a scheme, this is FINAL (forget about defaults)
+        $registry->register('http', $scheme_http);
+        $this->assertIdentical($registry->getScheme('http', $config), $scheme_http);
+        
+        // when we register a scheme, it's automatically allowed
+        $registry->register('foobar', $scheme_foobar);
+        $this->assertIdentical($registry->getScheme('foobar', $config), $scheme_foobar);
+        
+        // however, don't try to get a scheme that isn't allowed
+        $this->assertNull($registry->getScheme('ftp', $config));
         
     }