diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 1d654d9..b640f1e 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -701,6 +701,12 @@
 			{
 				$callable = TRUE;
 			}
+			elseif (is_array($rule) && isset($rule[0], $rule[1]) && is_callable($rule[1]))
+			{
+				// We have a "named" callable, so save the name
+				$callable = $rule[0];
+				$rule = $rule[1];
+			}
 
 			// Strip the parameter (if exists) from the rule
 			// Rules can contain a parameter: max_length[5]
@@ -712,7 +718,7 @@
 			}
 
 			// Call the function that corresponds to the rule
-			if ($callback OR $callable)
+			if ($callback OR $callable !== FALSE)
 			{
 				if ($callback)
 				{
@@ -730,8 +736,14 @@
 				else
 				{
 					$result = is_array($rule)
-						? $rule[0]->{$rule[1]}($postdata, $param)
-						: $rule($postdata, $param);
+						? $rule[0]->{$rule[1]}($postdata)
+						: $rule($postdata);
+
+					// Is $callable set to a rule name?
+					if ($callable !== FALSE)
+					{
+						$rule = $callable;
+					}
 				}
 
 				// Re-assign the result to the master data array
@@ -791,7 +803,7 @@
 			// Did the rule test negatively? If so, grab the error.
 			if ($result === FALSE)
 			{
-				// Callable rules don't have named error messages
+				// Callable rules might not have named error messages
 				if ( ! is_string($rule))
 				{
 					return;
diff --git a/user_guide_src/source/libraries/form_validation.rst b/user_guide_src/source/libraries/form_validation.rst
index 2ae56d2..2b7780f 100644
--- a/user_guide_src/source/libraries/form_validation.rst
+++ b/user_guide_src/source/libraries/form_validation.rst
@@ -505,11 +505,40 @@
 			'required',
 			function($value)
 			{
-				// Check $value and return TRUE/FALSE
+				// Check $value
 			}
 		)
 	);
 
+Of course, since a Callable rule by itself is not a string, it isn't
+a rule name either. That is a problem when you want to set error messages
+for them. In order to get around that problem, you can put such rules as
+the second element of an array, with the first one being the rule name::
+
+	$this->form_validation->set_rules(
+		'username', 'Username',
+		array(
+			'required',
+			array('username_callable', array($this->users_model', 'valid_username'))
+		)
+	);
+
+Anonymous function (PHP 5.3+) version::
+
+	$this->form_validation->set_rules(
+		'username', 'Username',
+		array(
+			'required',
+			array(
+				'username_callable',
+				function($str)
+				{
+					// Check validity of $str and return TRUE or FALSE
+				}
+			)
+		)
+	);
+
 .. _setting-error-messages:
 
 Setting Error Messages