diff --git a/src/wp-includes/customize/class-wp-customize-background-image-control.php b/src/wp-includes/customize/class-wp-customize-background-image-control.php
index b31a811f5f..e6b3ca6429 100644
--- a/src/wp-includes/customize/class-wp-customize-background-image-control.php
+++ b/src/wp-includes/customize/class-wp-customize-background-image-control.php
@@ -15,6 +15,13 @@
  * @see WP_Customize_Image_Control
  */
 class WP_Customize_Background_Image_Control extends WP_Customize_Image_Control {
+
+	/**
+	 * Customize control type.
+	 *
+	 * @since 4.1.0
+	 * @var string
+	 */
 	public $type = 'background';
 
 	/**
diff --git a/src/wp-includes/customize/class-wp-customize-background-image-setting.php b/src/wp-includes/customize/class-wp-customize-background-image-setting.php
index b8b1a06a9d..f56810e6aa 100644
--- a/src/wp-includes/customize/class-wp-customize-background-image-setting.php
+++ b/src/wp-includes/customize/class-wp-customize-background-image-setting.php
@@ -15,6 +15,13 @@
  * @see WP_Customize_Setting
  */
 final class WP_Customize_Background_Image_Setting extends WP_Customize_Setting {
+
+	/**
+	 * Unique string identifier for the setting.
+	 *
+	 * @since 3.4.0
+	 * @var string
+	 */
 	public $id = 'background_image_thumb';
 
 	/**
diff --git a/src/wp-includes/customize/class-wp-customize-header-image-control.php b/src/wp-includes/customize/class-wp-customize-header-image-control.php
index 82c1714261..98bf8af6d0 100644
--- a/src/wp-includes/customize/class-wp-customize-header-image-control.php
+++ b/src/wp-includes/customize/class-wp-customize-header-image-control.php
@@ -15,6 +15,7 @@
  * @see WP_Customize_Image_Control
  */
 class WP_Customize_Header_Image_Control extends WP_Customize_Image_Control {
+
 	/**
 	 * Customize control type.
 	 *
diff --git a/src/wp-includes/customize/class-wp-customize-header-image-setting.php b/src/wp-includes/customize/class-wp-customize-header-image-setting.php
index 7bbc923a40..d3792e0d14 100644
--- a/src/wp-includes/customize/class-wp-customize-header-image-setting.php
+++ b/src/wp-includes/customize/class-wp-customize-header-image-setting.php
@@ -17,6 +17,13 @@
  * @see WP_Customize_Setting
  */
 final class WP_Customize_Header_Image_Setting extends WP_Customize_Setting {
+
+	/**
+	 * Unique string identifier for the setting.
+	 *
+	 * @since 3.4.0
+	 * @var string
+	 */
 	public $id = 'header_image_data';
 
 	/**