diff --git a/system/language/english/form_validation_lang.php b/system/language/english/form_validation_lang.php
index cf1b3b5..6ff0cc2 100644
--- a/system/language/english/form_validation_lang.php
+++ b/system/language/english/form_validation_lang.php
@@ -42,6 +42,7 @@
 $lang['integer']				= 'The %s field must contain an integer.';
 $lang['regex_match']			= 'The %s field is not in the correct format.';
 $lang['matches']				= 'The %s field does not match the %s field.';
+$lang['differs']        		= 'The %s field must differ from the %s field.';
 $lang['is_unique'] 				= 'The %s field must contain a unique value.';
 $lang['is_natural']				= 'The %s field must only contain digits.';
 $lang['is_natural_no_zero']		= 'The %s field must only contain digits and must be greater than zero.';
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index fccc12a..6db5bb4 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -971,6 +971,19 @@
 	// --------------------------------------------------------------------
 
 	/**
+	 * Differs from another field
+	 *
+	 * @param	string
+	 * @param	string	field
+	 * @return	bool
+	 */
+	public function differs($str, $field)
+	{
+		return ! (isset($this->_field_data[$field]) && $this->_field_data[$field]['postdata'] === $str);
+	}
+
+	// --------------------------------------------------------------------
+	/**
 	 * Is Unique
 	 *
 	 * Check if the input value doesn't already exist
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index bfc2c95..b5f14d5 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -188,6 +188,7 @@
 	 -  Native PHP functions used as rules can now accept an additional parameter, other than the data itself.
 	 -  Updated set_rules() to accept an array of rules as well as a string.
 	 -  Fields that have empty rules set no longer run through validation (and therefore are not considered erroneous).
+	 -  Added new rule: ``differs``. It checks if the value of a field differs from the value of another field.
    -  Added support for setting :doc:`Table <libraries/table>` class defaults in a config file.
    -  Added a Wincache driver to the :doc:`Caching Library <libraries/caching>`.
    -  Added a Redis driver to the :doc:`Caching Library <libraries/caching>`.
diff --git a/user_guide_src/source/libraries/form_validation.rst b/user_guide_src/source/libraries/form_validation.rst
index 22272dc..6c6743d 100644
--- a/user_guide_src/source/libraries/form_validation.rst
+++ b/user_guide_src/source/libraries/form_validation.rst
@@ -872,6 +872,7 @@
 ========================= ========== ============================================================================================= =======================
 **required**              No         Returns FALSE if the form element is empty.                                                                          
 **matches**               Yes        Returns FALSE if the form element does not match the one in the parameter.                    matches[form_item]     
+**differs**               Yes        Returns FALSE if the form element does not differ from the one in the parameter.              differs[form_item]     
 **is_unique**             Yes        Returns FALSE if the form element is not unique to the table and field name in the            is_unique[table.field] 
                                      parameter. Note: This rule requires :doc:`Query Builder <../database/query_builder>` to be                             
                                      enabled in order to work.