diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index fb1c69c..db773e2 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -649,7 +649,12 @@
 			}
 			else
 			{
-				$postdata = $this->_field_data[$row['field']]['postdata'];
+				// If we get an array field, but it's not expected - then it is most likely
+				// somebody messing with the form on the client side, so we'll just consider
+				// it an empty field
+				$postdata = is_array($this->_field_data[$row['field']]['postdata'])
+						? NULL
+						: $this->_field_data[$row['field']]['postdata'];
 			}
 
 			// Is the rule a callback?
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index b39d43b..67b78bf 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -287,6 +287,7 @@
 -  Fixed a bug (#938) - :doc:`Config Library <libraries/config>` method site_url() added a question mark to the URL string when query strings are enabled even if it already existed.
 -  Fixed a bug (#999) - :doc:`Config Library <libraries/config>` method site_url() always appended ``$config['url_suffix']`` to the end of the URL string, regardless of wether a query string exists in it.
 -  Fixed a bug where :doc:`URL Helper <helpers/url_helper>` function anchor_popup() ignored the attributes argument if it is not an array.
+-  Fixed a bug (#1328) - :doc:`Form Validation Library <libraries/form_validation>` didn't properly check the type of the form fields before processing them.
 
 Version 2.1.1
 =============