diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 826d94f..9491f35 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -72,7 +72,7 @@
 		$this->CI->load->helper('form');
 
 		// Set the character encoding in MB.
-		if (function_exists('mb_internal_encoding'))
+		if (MB_ENABLED === TRUE)
 		{
 			mb_internal_encoding($this->CI->config->item('charset'));
 		}
@@ -950,7 +950,7 @@
 			return FALSE;
 		}
 
-		if (function_exists('mb_strlen'))
+		if (MB_ENABLED === TRUE)
 		{
 			return ! (mb_strlen($str) < $val);
 		}
@@ -974,7 +974,7 @@
 			return FALSE;
 		}
 
-		if (function_exists('mb_strlen'))
+		if (MB_ENABLED === TRUE)
 		{
 			return ! (mb_strlen($str) > $val);
 		}
@@ -998,7 +998,7 @@
 			return FALSE;
 		}
 
-		if (function_exists('mb_strlen'))
+		if (MB_ENABLED === TRUE)
 		{
 			return (mb_strlen($str) == $val);
 		}
diff --git a/system/libraries/Trackback.php b/system/libraries/Trackback.php
index 3bea5f9..be1de6f 100644
--- a/system/libraries/Trackback.php
+++ b/system/libraries/Trackback.php
@@ -141,7 +141,7 @@
 
 			$this->data['charset'] = ( ! isset($_POST['charset'])) ? 'auto' : strtoupper(trim($_POST['charset']));
 
-			if ($val != 'url' && function_exists('mb_convert_encoding'))
+			if ($val != 'url' && MB_ENABLED === TRUE)
 			{
 				$_POST[$val] = mb_convert_encoding($_POST[$val], $this->charset, $this->data['charset']);
 			}