diff --git a/library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php b/library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php
index f010cdfc..5b4ca1dc 100644
--- a/library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php
+++ b/library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php
@@ -48,6 +48,16 @@ class HTMLPurifier_ConfigSchema_InterchangeBuilder
             $type = explode('/', $hash->offsetGet('TYPE'));
             if (isset($type[1])) $directive->typeAllowsNull = true;
             $directive->type = $type[0];
+        } else {
+            throw new HTMLPurifier_ConfigSchema_Exception("TYPE in directive hash '{$directive->id}' not defined");
+        }
+        
+        if (isset($hash['DEFAULT'])) {
+            try {
+                $directive->default = $this->varParser->parse($hash->offsetGet('DEFAULT'), $directive->type, $directive->typeAllowsNull);
+            } catch (HTMLPurifier_VarParserException $e) {
+                throw new HTMLPurifier_ConfigSchema_Exception($e->getMessage() . " in DEFAULT in directive hash '{$directive->id}'");
+            }
         }
         
         if (isset($hash['DESCRIPTION'])) {
@@ -59,7 +69,15 @@ class HTMLPurifier_ConfigSchema_InterchangeBuilder
         }
         
         if (isset($hash['VALUE-ALIASES'])) {
-            $directive->valueAliases = $this->evalArray($hash->offsetGet('VALUE-ALIASES'));
+            $value_aliases = $this->evalArray($hash->offsetGet('VALUE-ALIASES'));
+            try {
+                foreach ($value_aliases as $alias => $real) {
+                    $directive->valueAliases[$this->varParser->parse($alias, $directive->type, $directive->typeAllowsNull)] =
+                        $this->varParser->parse($real, $directive->type, $directive->typeAllowsNull);
+                }
+            } catch (HTMLPurifier_VarParserException $e) {
+                throw new HTMLPurifier_ConfigSchema_Exception($e->getMessage() . " in $alias => $real in VALUE-ALIASES in directive hash '{$directive->id}'");
+            }
         }
         
         if (isset($hash['ALIASES'])) {
diff --git a/library/HTMLPurifier/ConfigSchema/Validator.php b/library/HTMLPurifier/ConfigSchema/Validator.php
index 88125877..d107623c 100644
--- a/library/HTMLPurifier/ConfigSchema/Validator.php
+++ b/library/HTMLPurifier/ConfigSchema/Validator.php
@@ -9,9 +9,18 @@ class HTMLPurifier_ConfigSchema_Validator
     protected $interchange;
     
     /**
-     * Volatile context variables to provide a fluent interface.
+     * Context-stack to provide easy to read error messages.
      */
-    protected $context = array(), $obj, $member;
+    protected $context = array();
+    
+    /**
+     * HTMLPurifier_VarParser to test variable types.
+     */
+    protected $parser;
+    
+    public function __construct() {
+        $this->parser = new HTMLPurifier_VarParser();
+    }
     
     /**
      * Validates a fully-formed interchange object. Throws an
@@ -38,17 +47,6 @@ class HTMLPurifier_ConfigSchema_Validator
         array_pop($this->context);
     }
     
-    public function validateDirective($d) {
-        $this->context[] = "directive '{$d->id}'";
-        $this->validateId($d->id);
-        $this->with($d, 'description')
-            ->assertNotEmpty();
-        if (!isset(HTMLPurifier_VarParser::$types[$d->type])) {
-            $this->error('type', 'is invalid');
-        }
-        array_pop($this->context);
-    }
-    
     public function validateId($id) {
         $this->context[] = "id '$id'";
         if (!isset($this->interchange->namespaces[$id->namespace])) {
@@ -63,6 +61,21 @@ class HTMLPurifier_ConfigSchema_Validator
         array_pop($this->context);
     }
     
+    public function validateDirective($d) {
+        $this->context[] = "directive '{$d->id}'";
+        $this->validateId($d->id);
+        $this->with($d, 'description')
+            ->assertNotEmpty();
+        $this->with($d, 'type')
+            ->assertNotEmpty();
+        if (!isset(HTMLPurifier_VarParser::$types[$d->type])) {
+            $this->error('type', 'is invalid');
+        }
+        $this->parser->parse($d->default, $d->type, $d->typeAllowsNull);
+        
+        array_pop($this->context);
+    }
+    
     // protected helper functions
     
     protected function with($obj, $member) {
diff --git a/library/HTMLPurifier/VarParser.php b/library/HTMLPurifier/VarParser.php
index bb0313f1..479d18ad 100644
--- a/library/HTMLPurifier/VarParser.php
+++ b/library/HTMLPurifier/VarParser.php
@@ -36,7 +36,7 @@ class HTMLPurifier_VarParser
      */
     final public function parse($var, $type, $allow_null = false) {
         if (!isset(HTMLPurifier_VarParser::$types[$type])) {
-            throw new HTMLPurifier_VarParserException("Invalid type $type");
+            throw new HTMLPurifier_VarParserException("Invalid type '$type'");
         }
         $var = $this->parseImplementation($var, $type, $allow_null);
         if ($allow_null && $var === null) return null;
@@ -73,7 +73,7 @@ class HTMLPurifier_VarParser
             case 'mixed':
                 return $var;
             default:
-                $this->errorInconsistent(__CLASS__, $type);
+                $this->errorInconsistent(get_class($this), $type);
         }
         $this->errorGeneric($var, $type);
     }
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/defaultType.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/defaultType.vtest
new file mode 100644
index 00000000..24ccbc61
--- /dev/null
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/defaultType.vtest
@@ -0,0 +1,9 @@
+ERROR: Expected type string, got integer in DEFAULT in directive hash 'Ns.Dir'
+----
+Ns
+DESCRIPTION: Namespace
+----
+Ns.Dir
+DESCRIPTION: Directive
+TYPE: string
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/descriptionNotEmpty.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/descriptionNotEmpty.vtest
index fd2d0922..5a6c1010 100644
--- a/tests/HTMLPurifier/ConfigSchema/Validator/directive/descriptionNotEmpty.vtest
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/descriptionNotEmpty.vtest
@@ -5,3 +5,4 @@ DESCRIPTION: Our namespace.
 ----
 Ns.Dir
 TYPE: int
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveAlnum.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveAlnum.vtest
index 9ffd143b..f659d430 100644
--- a/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveAlnum.vtest
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveAlnum.vtest
@@ -6,3 +6,4 @@ DESCRIPTION: Generic namespace.
 ID: Ns.+
 TYPE: int
 DESCRIPTION: Description
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveNotEmpty.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveNotEmpty.vtest
index 27e11282..bd936973 100644
--- a/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveNotEmpty.vtest
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/idDirectiveNotEmpty.vtest
@@ -6,3 +6,4 @@ DESCRIPTION: Our namespace
 ID: Ns.
 TYPE: int
 DESCRIPTION: Description.
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/idNamespaceExists.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/idNamespaceExists.vtest
index b216bf8d..fac07c66 100644
--- a/tests/HTMLPurifier/ConfigSchema/Validator/directive/idNamespaceExists.vtest
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/idNamespaceExists.vtest
@@ -3,3 +3,4 @@ ERROR: Namespace in id 'Rd.Dir' in directive 'Rd.Dir' does not exist
 ID: Rd.Dir
 TYPE: int
 DESCRIPTION: Description
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeDefined.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeDefined.vtest
new file mode 100644
index 00000000..d8023e9a
--- /dev/null
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeDefined.vtest
@@ -0,0 +1,8 @@
+ERROR: TYPE in directive hash 'Ns.Dir' not defined
+----
+Ns
+DESCRIPTION: Namespace
+----
+Ns.Dir
+DESCRIPTION: Notice that TYPE is missing
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeExists.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeExists.vtest
index dd2ae907..1b5d4197 100644
--- a/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeExists.vtest
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/typeExists.vtest
@@ -1,4 +1,4 @@
-ERROR: Type in directive 'Ns.Dir' is invalid
+ERROR: Invalid type 'foobar' in DEFAULT in directive hash 'Ns.Dir'
 ----
 Ns
 DESCRIPTION: Namespace
@@ -6,3 +6,4 @@ DESCRIPTION: Namespace
 Ns.Dir
 DESCRIPTION: Directive
 TYPE: foobar
+DEFAULT: 0
diff --git a/tests/HTMLPurifier/ConfigSchema/Validator/directive/unique.vtest b/tests/HTMLPurifier/ConfigSchema/Validator/directive/unique.vtest
index 7fbd4744..2ebeba23 100644
--- a/tests/HTMLPurifier/ConfigSchema/Validator/directive/unique.vtest
+++ b/tests/HTMLPurifier/ConfigSchema/Validator/directive/unique.vtest
@@ -3,7 +3,9 @@ ERROR: Cannot redefine directive 'Ns.Dir'
 ID: Ns.Dir
 DESCRIPTION: Version 1
 TYPE: int
+DEFAULT: 0
 ----
 ID: Ns.Dir
 DESCRIPTION: Version 2
 TYPE: int
+DEFAULT: 0