Index: library/Zend/Loader/PluginLoader.php
===================================================================
--- library/Zend/Loader/PluginLoader.php	(revision 14488)
+++ library/Zend/Loader/PluginLoader.php	(working copy)
@@ -145,7 +145,12 @@
         if ($this->_useStaticRegistry) {
             self::$_staticPrefixToPaths[$this->_useStaticRegistry][$prefix][] = $path;
         } else {
-            $this->_prefixToPaths[$prefix][] = $path;
+            if (!isset($this->_prefixToPaths[$prefix])) {
+                $this->_prefixToPaths[$prefix] = array();
+            }
+            if (!in_array($path, $this->_prefixToPaths[$prefix])) {
+                $this->_prefixToPaths[$prefix][] = $path;
+            }
         }
         return $this;
     }