diff --git a/wp-includes/option.php b/wp-includes/option.php
index 6134606471..9b3e884388 100644
--- a/wp-includes/option.php
+++ b/wp-includes/option.php
@@ -346,7 +346,8 @@ function update_option( $option, $value ) {
  * @param string         $option      Name of option to add. Expected to not be SQL-escaped.
  * @param mixed          $value       Optional. Option value. Must be serializable if non-scalar. Expected to not be SQL-escaped.
  * @param string         $deprecated  Optional. Description. Not used anymore.
- * @param string|bool    $autoload    Optional. Default is enabled. Whether to load the option when WordPress starts up.
+ * @param string|bool    $autoload    Optional. Whether to load the option when WordPress starts up.
+ *                                    Default is enabled. Accepts 'no' to disable for legacy reasons.
  * @return bool False if option was not added and true if option was added.
  */
 function add_option( $option, $value = '', $deprecated = '', $autoload = 'yes' ) {
@@ -373,7 +374,7 @@ function add_option( $option, $value = '', $deprecated = '', $autoload = 'yes' )
 			return false;
 
 	$serialized_value = maybe_serialize( $value );
-	$autoload = ( 'no' === $autoload ) ? 'no' : 'yes';
+	$autoload = ( 'no' === $autoload || false === $autoload ) ? 'no' : 'yes';
 
 	/**
 	 * Fires before an option is added.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index eb7e4c5b3c..6a8df66330 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31277';
+$wp_version = '4.2-alpha-31278';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.