diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index b0ba8bb..7056558 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -670,7 +670,11 @@
 			// Strip the parameter (if exists) from the rule
 			// Rules can contain a parameter: max_length[5]
 			$param = FALSE;
-			sscanf($rule, '%[^[][%[^]]', $rule, $param);
+			if (preg_match('/(.*?)\[(.*)\]/', $rule, $match))
+			{
+				$rule = $match[1];
+				$param = $match[2];
+			}
 
 			// Call the function that corresponds to the rule
 			if ($callback === TRUE)