Index: library/Zend/Validate/Sitemap/Lastmod.php
===================================================================
--- library/Zend/Validate/Sitemap/Lastmod.php	(revision 21296)
+++ library/Zend/Validate/Sitemap/Lastmod.php	(working copy)
@@ -44,12 +44,14 @@
      */
     const LASTMOD_REGEX = '/^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])(T([0-1][0-9]|2[0-3])(:[0-5][0-9])(:[0-5][0-9])?(\\+|-)([0-1][0-9]|2[0-3]):[0-5][0-9])?$/';
 
-    /**
+    /**#@+
      * Validation key for not valid
-     *
      */
     const NOT_VALID = 'invalidSitemapLastmod';
-
+    
+    const INVALID   = 'sitemapLastmodInvalid';
+    /**#@-*/
+    
     /**
      * Validation failure message template definitions
      *
@@ -57,6 +59,7 @@
      */
     protected $_messageTemplates = array(
         self::NOT_VALID => "'%value%' is no valid sitemap lastmod",
+        self::INVALID   => "Invalid type given, value should be string",
     );
 
     /**
@@ -69,12 +72,18 @@
      */
     public function isValid($value)
     {
-        $this->_setValue($value);
-
         if (!is_string($value)) {
+            $this->_error(self::INVALID);
             return false;
         }
-
-        return @preg_match(self::LASTMOD_REGEX, $value) == 1;
+        
+        $this->_setValue($value);
+        
+        if(!@preg_match(self::LASTMOD_REGEX, $value)) {
+            $this->_error(self::NOT_VALID);
+            return false;
+        }
+        
+        return true;
     }
 }
Index: library/Zend/Validate/Sitemap/Changefreq.php
===================================================================
--- library/Zend/Validate/Sitemap/Changefreq.php	(revision 21296)
+++ library/Zend/Validate/Sitemap/Changefreq.php	(working copy)
@@ -38,12 +38,14 @@
  */
 class Zend_Validate_Sitemap_Changefreq extends Zend_Validate_Abstract
 {
-    /**
+    /**#@+
      * Validation key for not valid
-     *
      */
     const NOT_VALID = 'invalidSitemapChangefreq';
-
+    
+    const INVALID   = 'sitemapChangefreqInvalid';
+    /**#@-*/
+    
     /**
      * Validation failure message template definitions
      *
@@ -51,6 +53,7 @@
      */
     protected $_messageTemplates = array(
         self::NOT_VALID => "'%value%' is no valid sitemap changefreq",
+        self::INVALID   => "Invalid type given, value should be string",
     );
 
     /**
@@ -73,12 +76,13 @@
      */
     public function isValid($value)
     {
-        $this->_setValue($value);
-
         if (!is_string($value)) {
+            $this->_error(self::INVALID);
             return false;
         }
-
+        
+        $this->_setValue($value);
+        
         if (!in_array($value, $this->_changeFreqs, true)) {
             $this->_error(self::NOT_VALID);
             return false;
Index: library/Zend/Validate/Sitemap/Loc.php
===================================================================
--- library/Zend/Validate/Sitemap/Loc.php	(revision 21296)
+++ library/Zend/Validate/Sitemap/Loc.php	(working copy)
@@ -43,12 +43,14 @@
  */
 class Zend_Validate_Sitemap_Loc extends Zend_Validate_Abstract
 {
-    /**
+    /**#@+
      * Validation key for not valid
-     *
      */
     const NOT_VALID = 'invalidSitemapLoc';
-
+    
+    const INVALID   = 'sitemapLocInvalid';
+    /**#@-*/
+    
     /**
      * Validation failure message template definitions
      *
@@ -56,6 +58,7 @@
      */
     protected $_messageTemplates = array(
         self::NOT_VALID => "'%value%' is no valid sitemap location",
+        self::INVALID   => "Invalid type given, value should be string",
     );
 
     /**
@@ -68,12 +71,18 @@
      */
     public function isValid($value)
     {
-        $this->_setValue($value);
-
         if (!is_string($value)) {
+            $this->_error(self::INVALID);
             return false;
         }
-
-        return Zend_Uri::check($value);
+        
+        $this->_setValue($value);
+        
+        if (!Zend_Uri::check($value)) {
+            $this->_error(self::NOT_VALID);
+            return false;
+        }
+        
+        return true;
     }
 }
Index: library/Zend/Validate/Sitemap/Priority.php
===================================================================
--- library/Zend/Validate/Sitemap/Priority.php	(revision 21296)
+++ library/Zend/Validate/Sitemap/Priority.php	(working copy)
@@ -38,12 +38,14 @@
  */
 class Zend_Validate_Sitemap_Priority extends Zend_Validate_Abstract
 {
-    /**
+    /**#@+
      * Validation key for not valid
-     *
      */
     const NOT_VALID = 'invalidSitemapPriority';
-
+    
+    const INVALID   = 'sitemapPriorityInvalid';
+    /**#@-*/
+    
     /**
      * Validation failure message template definitions
      *
@@ -51,6 +53,7 @@
      */
     protected $_messageTemplates = array(
         self::NOT_VALID => "'%value%' is no valid sitemap priority",
+        self::INVALID   => "Invalid type given, value should be numeric",
     );
 
     /**
@@ -63,13 +66,19 @@
      */
     public function isValid($value)
     {
-        $this->_setValue($value);
-
         if (!is_numeric($value)) {
+            $this->_error(self::INVALID);
             return false;
         }
-
+        
+        $this->_setValue($value);
         $value = (float)$value;
-        return $value >= 0 && $value <= 1;
+        
+        if ($value < 0 || $value > 1) {
+            $this->_error(self::NOT_VALID);
+            return false;
+        }
+        
+        return true;
     }
 }