diff --git a/framework/validators/CStringValidator.php b/framework/validators/CStringValidator.php
index 203fd429e..f628d9661 100644
--- a/framework/validators/CStringValidator.php
+++ b/framework/validators/CStringValidator.php
@@ -69,9 +69,17 @@ class CStringValidator extends CValidator
 			return;
 
 		if(function_exists('mb_strlen') && $this->encoding!==false)
-			$length=mb_strlen($value,$this->encoding ? $this->encoding : Yii::app()->charset);
+		{
+			if(!empty($this->encoding))
+				mb_strlen($value, $this->encoding);
+			else if(!empty(Yii::app()->charset))
+				$length=mb_strlen($value, Yii::app()->charset);
+			else
+				$length=strlen($value);
+		}
 		else
 			$length=strlen($value);
+
 		if($this->min!==null && $length<$this->min)
 		{
 			$message=$this->tooShort!==null?$this->tooShort:Yii::t('yii','{attribute} is too short (minimum is {min} characters).');