diff --git a/wp-includes/meta.php b/wp-includes/meta.php
index 22b03157ae..ac396a118b 100644
--- a/wp-includes/meta.php
+++ b/wp-includes/meta.php
@@ -22,7 +22,7 @@
  * @param string $meta_type Type of object metadata is for (e.g., comment, post, or user)
  * @param int $object_id ID of the object metadata is for
  * @param string $meta_key Metadata key
- * @param string $meta_value Metadata value
+ * @param mixed $meta_value Metadata value. Must be serializable if non-scalar.
  * @param bool $unique Optional, default is false. Whether the specified metadata key should be
  * 		unique for the object. If true, and the object already has a value for the specified
  * 		metadata key, no change will be made
@@ -93,8 +93,8 @@ function add_metadata($meta_type, $object_id, $meta_key, $meta_value, $unique =
  * @param string $meta_type Type of object metadata is for (e.g., comment, post, or user)
  * @param int $object_id ID of the object metadata is for
  * @param string $meta_key Metadata key
- * @param string $meta_value Metadata value
- * @param string $prev_value Optional. If specified, only update existing metadata entries with
+ * @param mixed $meta_value Metadata value. Must be serializable if non-scalar.
+ * @param mixed $prev_value Optional. If specified, only update existing metadata entries with
  * 		the specified value. Otherwise, update all entries.
  * @return bool True on successful update, false on failure.
  */
@@ -174,7 +174,7 @@ function update_metadata($meta_type, $object_id, $meta_key, $meta_value, $prev_v
  * @param string $meta_type Type of object metadata is for (e.g., comment, post, or user)
  * @param int $object_id ID of the object metadata is for
  * @param string $meta_key Metadata key
- * @param string $meta_value Optional. Metadata value. If specified, only delete metadata entries
+ * @param mixed $meta_value Optional. Metadata value. Must be serializable if non-scalar. If specified, only delete metadata entries
  * 		with this value. Otherwise, delete all entries with the specified meta_key.
  * @param bool $delete_all Optional, default is false. If true, delete matching metadata entries
  * 		for all objects, ignoring the specified object_id. Otherwise, only delete matching
@@ -720,8 +720,8 @@ class WP_Meta_Query {
 				$key_only_queries[$k] = $q;
 				unset( $this->queries[$k] );
 			}
-		}		
-		
+		}
+
 		// Split out the meta_key only queries (we can only do this for OR)
 		if ( 'OR' == $this->relation ) {
 			foreach ( $this->queries as $k => $q ) {
diff --git a/wp-includes/option.php b/wp-includes/option.php
index 385ba89253..eabb677525 100644
--- a/wp-includes/option.php
+++ b/wp-includes/option.php
@@ -208,7 +208,7 @@ function wp_load_core_site_options( $site_id = null ) {
  * @uses do_action() Calls 'update_option_$option' and 'updated_option' hooks on success.
  *
  * @param string $option Option name. Expected to not be SQL-escaped.
- * @param mixed $newvalue Option value. Expected to not be SQL-escaped.
+ * @param mixed $newvalue Option value. Must be serializable if non-scalar. Expected to not be SQL-escaped.
  * @return bool False if value was not updated and true if value was updated.
  */
 function update_option( $option, $newvalue ) {
@@ -284,7 +284,7 @@ function update_option( $option, $newvalue ) {
  * @uses do_action() Calls 'add_option_$option' and 'added_option' hooks on success.
  *
  * @param string $option Name of option to add. Expected to not be SQL-escaped.
- * @param mixed $value Optional. Option value, can be anything. 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 mixed $deprecated Optional. Description. Not used anymore.
  * @param bool $autoload Optional. Default is enabled. Whether to load the option when WordPress starts up.
  * @return bool False if option was not added and true if option was added.
@@ -488,7 +488,7 @@ function get_transient( $transient ) {
  * @uses do_action() Calls 'set_transient_$transient' and 'setted_transient' hooks on success.
  *
  * @param string $transient Transient name. Expected to not be SQL-escaped.
- * @param mixed $value Transient value. Expected to not be SQL-escaped.
+ * @param mixed $value Transient value. Must be serializable if non-scalar. Expected to not be SQL-escaped.
  * @param int $expiration Time until expiration in seconds, default 0
  * @return bool False if value was not set and true if value was set.
  */
diff --git a/wp-includes/post.php b/wp-includes/post.php
index a22765c7d3..5eea14e3bb 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -1671,7 +1671,7 @@ function get_posts($args = null) {
  *
  * @param int $post_id Post ID.
  * @param string $meta_key Metadata name.
- * @param mixed $meta_value Metadata value.
+ * @param mixed $meta_value Metadata value. Must be serializable if non-scalar.
  * @param bool $unique Optional, default is false. Whether the same key should not be added.
  * @return int|bool Meta ID on success, false on failure.
  */
@@ -1695,7 +1695,7 @@ function add_post_meta($post_id, $meta_key, $meta_value, $unique = false) {
  *
  * @param int $post_id post ID
  * @param string $meta_key Metadata name.
- * @param mixed $meta_value Optional. Metadata value.
+ * @param mixed $meta_value Optional. Metadata value. Must be serializable if non-scalar.
  * @return bool True on success, false on failure.
  */
 function delete_post_meta($post_id, $meta_key, $meta_value = '') {
@@ -1735,7 +1735,7 @@ function get_post_meta($post_id, $key = '', $single = false) {
  *
  * @param int $post_id Post ID.
  * @param string $meta_key Metadata key.
- * @param mixed $meta_value Metadata value.
+ * @param mixed $meta_value Metadata value. Must be serializable if non-scalar.
  * @param mixed $prev_value Optional. Previous value to check before removing.
  * @return bool True on success, false on failure.
  */