Fixed a bug in the URL Helper where prep_url() could cause a PHP error on PHP versions < 5.1.2.
diff --git a/system/helpers/url_helper.php b/system/helpers/url_helper.php
index 7707d68..dad7611 100644
--- a/system/helpers/url_helper.php
+++ b/system/helpers/url_helper.php
@@ -446,7 +446,9 @@
 			return '';
 		}
 
-		if ( ! parse_url($str, PHP_URL_SCHEME))
+		$url = parse_url($str);
+		
+		if ( ! $url OR ! isset($url['scheme']))
 		{
 			$str = 'http://'.$str;
 		}
diff --git a/user_guide/changelog.html b/user_guide/changelog.html
index 5740f73..9bb4a4e 100644
--- a/user_guide/changelog.html
+++ b/user_guide/changelog.html
@@ -184,6 +184,7 @@
 	<li>Fixed a bug where getimagesize() was being needlessly checked on non-image files in is_allowed_type().</li>
 	<li>Fixed a bug in the Encryption library where an empty key was not triggering an error.</li>
 	<li>Fixed a bug in the Email library where CC and BCC recipients were not reset when using the clear() method (#109).</li>
+	<li>Fixed a bug in the URL Helper where prep_url() could cause a PHP error on PHP versions &lt; 5.1.2.</li>
 </ul>
 
 <h2>Version 1.7.2</h2>