Index: library/Zend/Controller/Action.php
===================================================================
--- library/Zend/Controller/Action.php	(revision 22458)
+++ library/Zend/Controller/Action.php	(working copy)
@@ -580,7 +580,7 @@
     protected function _getParam($paramName, $default = null)
     {
         $value = $this->getRequest()->getParam($paramName);
-        if ((null === $value) && (null !== $default)) {
+		 if ((null === $value || '' === $value) && (null !== $default)) {
             $value = $default;
         }
 
Index: tests/Zend/Controller/ActionTest.php
===================================================================
--- tests/Zend/Controller/ActionTest.php	(revision 22458)
+++ tests/Zend/Controller/ActionTest.php	(working copy)
@@ -245,6 +245,15 @@
         $this->assertEquals(0, $this->_controller->getParam('bar', -1));
         $this->assertEquals(-1, $this->_controller->getParam('baz', -1));
     }
+	
+	/**
+     * @group ZF-9179
+     */
+	public function testGetParamForEmptyString()
+	{
+		$this->_controller->setParam('lang', '');
+		$this->assertEquals('en', $this->_controller->getParam('lang', 'en'));
+	}
 
     public function testGetParams()
     {