diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 61f0298..c39b65d 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -1229,9 +1229,9 @@
 	 */
 	public function valid_email($str)
 	{
-		if (function_exists('idn_to_ascii') && $atpos = strpos($str, '@'))
+		if (function_exists('idn_to_ascii') && sscanf($str, '%[^@]@%s', $name, $domain) === 2)
 		{
-			$str = substr($str, 0, ++$atpos).idn_to_ascii(substr($str, $atpos));
+			$str = $name.'@'.idn_to_ascii($domain);
 		}
 
 		return (bool) filter_var($str, FILTER_VALIDATE_EMAIL);