diff --git a/system/core/URI.php b/system/core/URI.php
index a997525..208d311 100644
--- a/system/core/URI.php
+++ b/system/core/URI.php
@@ -278,7 +278,7 @@
 		{
 			// preg_quote() in PHP 5.3 escapes -, so the str_replace() and addition of - to preg_quote() is to maintain backwards
 			// compatibility as many are unaware of how characters in the permitted_uri_chars will be parsed as a regex pattern
-			if ( ! preg_match('|^['.str_replace(array('\\-', '\-'), '-', preg_quote($this->config->item('permitted_uri_chars'), '-')).']+$|i', $str))
+			if ( ! preg_match('|^['.str_replace(array('\\-', '\-'), '-', preg_quote($this->config->item('permitted_uri_chars'), '-')).']+$|i', urldecode($str)))
 			{
 				show_error('The URI you submitted has disallowed characters.', 400);
 			}