diff --git a/cake/libs/validation.php b/cake/libs/validation.php
index fce432afa..e42bf4d02 100644
--- a/cake/libs/validation.php
+++ b/cake/libs/validation.php
@@ -124,6 +124,10 @@ class Validation extends Object {
 			$this->_extract($check);
 		}
 
+		if(empty($this->check)) {
+			return false;
+		}
+
 		$this->regex = '/[^\\dA-Z]/i';
 		if($this->_check() === true){
 			return false;
diff --git a/cake/tests/cases/libs/validation.test.php b/cake/tests/cases/libs/validation.test.php
index 15a3ddcbc..0d98bb8b4 100644
--- a/cake/tests/cases/libs/validation.test.php
+++ b/cake/tests/cases/libs/validation.test.php
@@ -47,6 +47,7 @@ class ValidationTestCase extends UnitTestCase {
 		$this->assertFalse($validation->alphaNumeric("\t"));
 		$this->assertFalse($validation->alphaNumeric("\r"));
 		$this->assertFalse($validation->alphaNumeric(' '));
+		$this->assertFalse($validation->alphaNumeric(''));
 	}
 
 	function testAlphaNumericPassedAsArray(){
@@ -61,6 +62,7 @@ class ValidationTestCase extends UnitTestCase {
 		$this->assertFalse($validation->alphaNumeric(array('check' => "\t")));
 		$this->assertFalse($validation->alphaNumeric(array('check' => "\r")));
 		$this->assertFalse($validation->alphaNumeric(array('check' =>  ' ')));
+		$this->assertFalse($validation->alphaNumeric(array('check' =>  '')));
 	}
 
 	function testBetween(){