diff --git a/system/helpers/form_helper.php b/system/helpers/form_helper.php
index fd80776..37dafd9 100644
--- a/system/helpers/form_helper.php
+++ b/system/helpers/form_helper.php
@@ -769,12 +769,11 @@
 		{
 			return $CI->form_validation->set_checkbox($field, $value, $default);
 		}
-		elseif (($input = $CI->input->post($field, FALSE)) === NULL)
-		{
-			return ($default === TRUE) ? ' checked="checked"' : '';
-		}
 
+		// Form inputs are always strings ...
 		$value = (string) $value;
+		$input = $CI->input->post($field, FALSE);
+
 		if (is_array($input))
 		{
 			// Note: in_array('', array(0)) returns TRUE, do not use it
@@ -789,7 +788,13 @@
 			return '';
 		}
 
-		return ($input === $value) ? ' checked="checked"' : '';
+		// Unchecked checkbox and radio inputs are not even submitted by browsers ...
+		if ($CI->input->method() === 'post')
+		{
+			return ($input === 'value') ? ' checked="checked"' : '';
+		}
+
+		return ($default === TRUE) ? ' checked="checked"' : '';
 	}
 }
 
@@ -816,12 +821,32 @@
 		{
 			return $CI->form_validation->set_radio($field, $value, $default);
 		}
-		elseif (($input = $CI->input->post($field, FALSE)) === NULL)
+
+		// Form inputs are always strings ...
+		$value = (string) $value;
+		$input = $CI->input->post($field, FALSE);
+
+		if (is_array($input))
 		{
-			return ($default === TRUE) ? ' checked="checked"' : '';
+			// Note: in_array('', array(0)) returns TRUE, do not use it
+			foreach ($input as &$v)
+			{
+				if ($value === $v)
+				{
+					return ' checked="checked"';
+				}
+			}
+
+			return '';
 		}
 
-		return ($input === (string) $value) ? ' checked="checked"' : '';
+		// Unchecked checkbox and radio inputs are not even submitted by browsers ...
+		if ($CI->input->method() === 'post')
+		{
+			return ($input === 'value') ? ' checked="checked"' : '';
+		}
+
+		return ($default === TRUE) ? ' checked="checked"' : '';
 	}
 }
 
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index f632f72..2b0f51b 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -11,6 +11,7 @@
 -------------------
 
 -  Fixed a bug (#4212) - :doc:`Query Builder <database/query_builder>` method ``count_all_results()`` could fail if an ``ORDER BY`` condition is used.
+-  Fixed a bug where :doc:`Form Helper <helpers/form_helper>` functions `set_checkbox()`, `set_radio()` didn't "uncheck" inputs on a submitted form if the default state is "checked".
 
 Version 3.0.3
 =============