diff --git a/system/core/Utf8.php b/system/core/Utf8.php
index ff3e491..b58c611 100644
--- a/system/core/Utf8.php
+++ b/system/core/Utf8.php
@@ -59,17 +59,31 @@
 		{
 			define('MB_ENABLED', TRUE);
 			mb_internal_encoding($charset);
+			// This is required for mb_convert_encoding() to strip invalid characters
+			ini_set('mbstring.substitute_character', 'none');
 		}
 		else
 		{
 			define('MB_ENABLED', FALSE);
 		}
 
+		// Do the same for iconv, which actually has more easy to remember
+		// predefined constants (such as ICONV_IMPL), but the iconv PHP
+		// manual page says that using them is "strongly discouraged".
+		if (extension_loaded('iconv'))
+		{
+			define('ICONV_ENABLED', TRUE);
+			iconv_set_encoding('internal_encoding', $charset);
+		}
+		else
+		{
+			define('ICONV_ENABLED', FALSE);
+		}
+
 		if (
-			defined('PREG_BAD_UTF8_ERROR')	// PCRE must support UTF-8
-			&& function_exists('iconv')	// iconv must be installed
-			&& MB_ENABLED === TRUE		// mbstring must be enabled
-			&& $charset === 'UTF-8'		// Application charset must be UTF-8
+			defined('PREG_BAD_UTF8_ERROR')				// PCRE must support UTF-8
+			&& (ICONV_ENABLED === TRUE OR MB_ENABLED === TRUE)	// iconv or mbstring must be installed
+			&& $charset === 'UTF-8'					// Application charset must be UTF-8
 			)
 		{
 			define('UTF8_ENABLED', TRUE);
@@ -98,7 +112,14 @@
 	{
 		if ($this->_is_ascii($str) === FALSE)
 		{
-			$str = @iconv('UTF-8', 'UTF-8//IGNORE', $str);
+			if (ICONV_ENABLED)
+			{
+				$str = @iconv('UTF-8', 'UTF-8//IGNORE', $str);
+			}
+			elseif (MB_ENABLED)
+			{
+				$str = mb_convert_encoding($str, 'UTF-8', 'UTF-8');
+			}
 		}
 
 		return $str;
@@ -134,7 +155,7 @@
 	 */
 	public function convert_to_utf8($str, $encoding)
 	{
-		if (function_exists('iconv'))
+		if (ICONV_ENABLED)
 		{
 			return @iconv($encoding, 'UTF-8', $str);
 		}
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 7d13a46..93c19de 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -1544,7 +1544,7 @@
 			{
 				return mb_encode_mimeheader($str, $this->charset, 'Q', $this->crlf);
 			}
-			elseif (extension_loaded('iconv'))
+			elseif (ICONV_ENABLED === TRUE)
 			{
 				$output = @iconv_mime_encode('', $str,
 					array(
@@ -1573,9 +1573,9 @@
 		isset($chars) OR $chars = strlen($str);
 
 		$output = '=?'.$this->charset.'?Q?';
-		for ($i = 0, $length = strlen($output), $iconv = extension_loaded('iconv'); $i < $chars; $i++)
+		for ($i = 0, $length = strlen($output); $i < $chars; $i++)
 		{
-			$chr = ($this->charset === 'UTF-8' && $iconv === TRUE)
+			$chr = ($this->charset === 'UTF-8' && ICONV_ENABLED === TRUE)
 				? '='.implode('=', str_split(strtoupper(bin2hex(iconv_substr($str, $i, 1, $this->charset))), 2))
 				: '='.strtoupper(bin2hex($str[$i]));
 
diff --git a/system/libraries/Trackback.php b/system/libraries/Trackback.php
index 7bcb2aa..9fa4a8e 100644
--- a/system/libraries/Trackback.php
+++ b/system/libraries/Trackback.php
@@ -181,7 +181,14 @@
 
 			if ($val !== 'url' && MB_ENABLED === TRUE)
 			{
-				$_POST[$val] = mb_convert_encoding($_POST[$val], $this->charset, $this->data['charset']);
+				if (MB_ENABLED === TRUE)
+				{
+					$_POST[$val] = mb_convert_encoding($_POST[$val], $this->charset, $this->data['charset']);
+				}
+				elseif (ICONV_ENABLED === TRUE)
+				{
+					$_POST[$val] = @iconv($this->data['charset'], $this->charset.'//IGNORE', $_POST[$val]);
+				}
 			}
 
 			$_POST[$val] = ($val !== 'url') ? $this->convert_xml(strip_tags($_POST[$val])) : strip_tags($_POST[$val]);
diff --git a/tests/mocks/core/utf8.php b/tests/mocks/core/utf8.php
index a43138f..9dda43a 100644
--- a/tests/mocks/core/utf8.php
+++ b/tests/mocks/core/utf8.php
@@ -16,11 +16,22 @@
 		{
 			defined('MB_ENABLED') OR define('MB_ENABLED', TRUE);
 			mb_internal_encoding('UTF-8');
+			ini_set('mbstring.substitute_character', 'none');
 		}
 		else
 		{
 			defined('MB_ENABLED') OR define('MB_ENABLED', FALSE);
 		}
+
+		if (extension_loaded('iconv'))
+		{
+			defined('ICONV_ENABLED') OR define('ICONV_ENABLED', TRUE);
+			iconv_set_encoding('internal_encoding', 'UTF-8');
+		}
+		else
+		{
+			defined('ICONV_ENABLED') OR define('ICONV_ENABLED', FALSE);
+		}
 	}
 
 	public function is_ascii_test($str)
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 9e63a68..b5b31dc 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -396,6 +396,7 @@
       - Added support for setting table class defaults in a config file.
 
    -  :doc:`Zip Library <libraries/zip>` method ``read_file()`` can now also alter the original file path/name while adding files to an archive.
+   -  :doc:`Trackback Library <libraries/trackback>` method ``receive()`` will now utilize ``iconv()`` if it is available but ``mb_convert_encoding()`` is not.
 
 -  Core
 
@@ -489,9 +490,15 @@
       -  Language files are now loaded in a cascading style with the one in **system/** always loaded and overriden afterwards, if another one is found.
 
    -  :doc:`Hooks Library <general/hooks>` changes include:
+
       -  Renamed method ``_call_hook()`` to ``call_hook()``.
       -  Class instances are now stored in order to maintain their state.
 
+   -  UTF-8 Library changes include:
+
+      -  ``UTF8_ENABLED`` now requires only one of `Multibyte String <http://php.net/mbstring>`_ or `iconv <http://php.net/iconv>`_ to be available instead of both.
+      -  Changed method ``clean_string()`` to utilize ``mb_convert_encoding()`` if it is available but ``iconv()`` is not.
+
    -  Removed ``CI_CORE`` boolean constant from *CodeIgniter.php* (no longer Reactor and Core versions).
    -  Log Library will now try to create the **log_path** directory if it doesn't exist.
    -  Added support for HTTP-Only cookies with new config option *cookie_httponly* (default FALSE).
diff --git a/user_guide_src/source/general/reserved_names.rst b/user_guide_src/source/general/reserved_names.rst
index a767651..81a05ac 100644
--- a/user_guide_src/source/general/reserved_names.rst
+++ b/user_guide_src/source/general/reserved_names.rst
@@ -61,6 +61,9 @@
 -  APPPATH
 -  VIEWPATH
 -  CI_VERSION
+-  MB_ENABLED
+-  ICONV_ENABLED
+-  UTF8_ENABLED
 -  FILE_READ_MODE
 -  FILE_WRITE_MODE
 -  DIR_READ_MODE