diff --git a/core-bundle/src/Resources/contao/library/Contao/Validator.php b/core-bundle/src/Resources/contao/library/Contao/Validator.php
index <HASH>..<HASH> 100644
--- a/core-bundle/src/Resources/contao/library/Contao/Validator.php
+++ b/core-bundle/src/Resources/contao/library/Contao/Validator.php
@@ -324,6 +324,6 @@ class Validator
 	 */
 	public static function isGooglePlusId($varValue)
 	{
-		return preg_match('/^([0-9]{21}|\+[\pN\pL-]+)$/u', $varValue);
+		return preg_match('/^([0-9]{21}|\+[\pN\pL_-]+)$/u', $varValue);
 	}
 }
[Core] Handle underscores in the Google+ vanity name (see #<I>)