diff --git a/library/Zend/Form.php b/library/Zend/Form.php
index 5e6544f..b7aa18a 100644
--- a/library/Zend/Form.php
+++ b/library/Zend/Form.php
@@ -495,12 +495,13 @@ class Zend_Form implements Iterator, Countable, Zend_Validate_Interface
                 $loader->addPrefixPath($prefix, $path);
                 return $this;
             case null:
-                $prefix = rtrim($prefix, '_');
+                $nsSeparator = (false !== strpos($prefix, '\\'))?'\\':'_';
+                $prefix = rtrim($prefix, $nsSeparator);
                 $path   = rtrim($path, DIRECTORY_SEPARATOR);
                 foreach (array(self::DECORATOR, self::ELEMENT) as $type) {
                     $cType        = ucfirst(strtolower($type));
                     $pluginPath   = $path . DIRECTORY_SEPARATOR . $cType . DIRECTORY_SEPARATOR;
-                    $pluginPrefix = $prefix . '_' . $cType;
+                    $pluginPrefix = $prefix . $nsSeparator . $cType;
                     $loader       = $this->getPluginLoader($type);
                     $loader->addPrefixPath($pluginPrefix, $pluginPath);
                 }
diff --git a/library/Zend/Form/Element.php b/library/Zend/Form/Element.php
index 42cf95b..4213d8a 100644
--- a/library/Zend/Form/Element.php
+++ b/library/Zend/Form/Element.php
@@ -1070,12 +1070,13 @@ class Zend_Form_Element implements Zend_Validate_Interface
                 $loader->addPrefixPath($prefix, $path);
                 return $this;
             case null:
-                $prefix = rtrim($prefix, '_');
+                $nsSeparator = (false !== strpos($prefix, '\\'))?'\\':'_';
+                $prefix = rtrim($prefix, $nsSeparator);
                 $path   = rtrim($path, DIRECTORY_SEPARATOR);
                 foreach (array(self::DECORATOR, self::FILTER, self::VALIDATE) as $type) {
                     $cType        = ucfirst(strtolower($type));
                     $pluginPath   = $path . DIRECTORY_SEPARATOR . $cType . DIRECTORY_SEPARATOR;
-                    $pluginPrefix = $prefix . '_' . $cType;
+                    $pluginPrefix = $prefix . $nsSeparator . $cType;
                     $loader       = $this->getPluginLoader($type);
                     $loader->addPrefixPath($pluginPrefix, $pluginPath);
                 }
diff --git a/library/Zend/Form/Element/Captcha.php b/library/Zend/Form/Element/Captcha.php
index 25ad94b..ecdb710 100644
--- a/library/Zend/Form/Element/Captcha.php
+++ b/library/Zend/Form/Element/Captcha.php
@@ -244,7 +244,8 @@ class Zend_Form_Element_Captcha extends Zend_Form_Element_Xhtml
         switch ($type) {
             case null:
                 $loader = $this->getPluginLoader(self::CAPTCHA);
-                $cPrefix = rtrim($prefix, '_') . '_Captcha';
+                $nsSeparator = (false !== strpos($prefix, '\\'))?'\\':'_';
+                $cPrefix = rtrim($prefix, $nsSeparator) . $nsSeparator . 'Captcha';
                 $cPath   = rtrim($path, '/\\') . '/Captcha';
                 $loader->addPrefixPath($cPrefix, $cPath);
                 return parent::addPrefixPath($prefix, $path);
diff --git a/library/Zend/Form/Element/File.php b/library/Zend/Form/Element/File.php
index 7ef9421..3d0be60 100644
--- a/library/Zend/Form/Element/File.php
+++ b/library/Zend/Form/Element/File.php
@@ -150,7 +150,8 @@ class Zend_Form_Element_File extends Zend_Form_Element_Xhtml
         }
 
         if (empty($type)) {
-            $pluginPrefix = rtrim($prefix, '_') . '_Transfer_Adapter';
+            $nsSeparator = (false !== strpos($prefix, '\\'))?'\\':'_';
+            $pluginPrefix = rtrim($prefix, $nsSeparator) . $nsSeparator . 'Transfer' . $nsSeparator . 'Adapter';
             $pluginPath   = rtrim($path, DIRECTORY_SEPARATOR) . '/Transfer/Adapter/';
             $loader       = $this->getPluginLoader(self::TRANSFER_ADAPTER);
             $loader->addPrefixPath($pluginPrefix, $pluginPath);
diff --git a/library/Zend/Loader/PluginLoader.php b/library/Zend/Loader/PluginLoader.php
index f74ad9e..fceb838 100644
--- a/library/Zend/Loader/PluginLoader.php
+++ b/library/Zend/Loader/PluginLoader.php
@@ -127,12 +127,8 @@ class Zend_Loader_PluginLoader implements Zend_Loader_PluginLoader_Interface
             return $prefix;
         }
 
-        $last = strlen($prefix) - 1;
-        if ($prefix{$last} == '\\') {
-            return $prefix;
-        }
-
-        return rtrim($prefix, '_') . '_';
+        $nsSeparator = (false !== strpos($prefix, '\\'))?'\\':'_';
+        return rtrim($prefix, $nsSeparator) . $nsSeparator;
     }
 
     /**