Index: library/Zend/Session/Namespace.php
===================================================================
--- library/Zend/Session/Namespace.php	(revision 13200)
+++ library/Zend/Session/Namespace.php	(working copy)
@@ -98,6 +98,14 @@
             throw new Zend_Session_Exception('Session namespace must not start with an underscore.');
         }
 
+        if (preg_match('#(^[0-9])#i', $namespace[0])) {
+            /**
+             * @see Zend_Session_Exception
+             */
+            require_once 'Zend/Session/Exception.php';
+            throw new Zend_Session_Exception('Session namespace must not start with a number.');
+        }
+
         if (isset(self::$_singleInstances[$namespace])) {
             /**
              * @see Zend_Session_Exception
Index: tests/Zend/Session/SessionTest.php
===================================================================
--- tests/Zend/Session/SessionTest.php	(revision 13200)
+++ tests/Zend/Session/SessionTest.php	(working copy)
@@ -375,6 +375,23 @@
     }
 
     /**
+     * test for detection of illegal namespace names; expect exception complaining about name beginning
+     * with an underscore
+     *
+     * @return void
+     */
+    public function testInitNamespaceNumber()
+    {
+        try {
+            $s = new Zend_Session_Namespace('0namespace');
+            $this->fail('No exception was returned when requesting a namespace having a name beginning with '
+                . 'a number');
+        } catch (Zend_Session_Exception $e) {
+            $this->assertRegexp('/number/i', $e->getMessage());
+        }
+    }
+
+    /**
      * test iteration; expect native PHP foreach statement is able to properly iterate all items in a session namespace
      *
      * @return void