diff --git a/includes/acf-value-functions.php b/includes/acf-value-functions.php
index 99c3e07..637a7fa 100644
--- a/includes/acf-value-functions.php
+++ b/includes/acf-value-functions.php
@@ -192,7 +192,7 @@ function acf_format_value( $value, $post_id, $field, $escape_html = false ) {
  * @param   mixed        $value   The new value.
  * @param   (int|string) $post_id The post id.
  * @param   array        $field   The field array.
- * @return  boolean
+ * @return  int|boolean Meta ID if the key didn't exist, true on successful update, false on failure.
  */
 function acf_update_value( $value, $post_id, $field ) {
 
diff --git a/includes/api/api-template.php b/includes/api/api-template.php
index 11e6d75..f625f76 100644
--- a/includes/api/api-template.php
+++ b/includes/api/api-template.php
@@ -1133,7 +1133,7 @@ function acf_shortcode( $atts ) {
  * @param mixed  $value    The value to save in the database.
  * @param mixed  $post_id  The post_id of which the value is saved against.
  *
- * @return boolean
+ * @return int|boolean Meta ID if the key didn't exist, true on successful update, false on failure.
  */
 function update_field( $selector, $value, $post_id = false ) {
 
@@ -1168,7 +1168,7 @@ function update_field( $selector, $value, $post_id = false ) {
  * @param   $value (mixed) the value to save in the database
  * @param   $post_id (mixed) the post_id of which the value is saved against
  *
- * @return  boolean
+ * @return  int|boolean Meta ID if the key didn't exist, true on successful update, false on failure.
  */
 function update_sub_field( $selector, $value, $post_id = false ) {