diff --git a/system/core/URI.php b/system/core/URI.php
index 2211e36..b6eff1f 100644
--- a/system/core/URI.php
+++ b/system/core/URI.php
@@ -201,7 +201,9 @@
 			return '';
 		}
 
-		$uri = parse_url($_SERVER['REQUEST_URI']);
+		// parse_url() returns false if no host is present, but the path or query string
+		// contains a colon followed by a number
+		$uri = parse_url('dummy'.$_SERVER['REQUEST_URI']);
 		$query = isset($uri['query']) ? $uri['query'] : '';
 		$uri = isset($uri['path']) ? $uri['path'] : '';
 
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 1621c43..b5256b7 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -72,6 +72,7 @@
 -  Fixed a bug (#3991) - ``$config['rewrite_short_tags']`` never worked due to ``function_exists('eval')`` always returning FALSE.
 -  Fixed a bug where the :doc:`File Uploadin Library <libraries/file_uploading>` library will not properly configure its maximum file size unless the input value is of type integer.
 -  Fixed a bug (#4000) - :doc:`Pagination Library <libraries/pagination>` didn't enable "rel" attributes by default if no attributes-related config options were used.
+-  Fixed a bug (#4004) - :doc:`URI Class <libraries/uri>` didn't properly parse the request URI if it contains a colon followed by a digit.
 
 Version 3.0.0
 =============