diff --git a/wp-admin/custom-background.php b/wp-admin/custom-background.php
index d024c9a4aa..ea54cbc27f 100644
--- a/wp-admin/custom-background.php
+++ b/wp-admin/custom-background.php
@@ -172,37 +172,37 @@ if ( $this->admin_image_div_callback ) {
 <tr>
 <td><fieldset><legend class="screen-reader-text"><span><?php _e( 'Position' ); ?></span></legend>
 <label>
-<input name="background-position" type="radio" value="left" <?php checked('left', get_theme_mod('background_position')); ?> />
+<input name="background-position" type="radio" value="left" <?php checked('left', get_theme_mod('background_position', 'left')); ?> />
 <?php _e('Left') ?>
 </label>
 <label>
-<input name="background-position" type="radio" value="center" <?php checked('center', get_theme_mod('background_position')); ?> />
+<input name="background-position" type="radio" value="center" <?php checked('center', get_theme_mod('background_position', 'left')); ?> />
 <?php _e('Center') ?>
 </label>
 <label>
-<input name="background-position" type="radio" value="right" <?php checked('right', get_theme_mod('background_position')); ?> />
+<input name="background-position" type="radio" value="right" <?php checked('right', get_theme_mod('background_position', 'left')); ?> />
 <?php _e('Right') ?>
 </label>
 </fieldset></td>
 
 <td><fieldset><legend class="screen-reader-text"><span><?php _e( 'Repeat' ); ?></span></legend>
 <label>
-<input name="background-repeat" type="radio" value="no-repeat" <?php checked('no-repeat', get_theme_mod('background_repeat')); ?> />
+<input name="background-repeat" type="radio" value="no-repeat" <?php checked('no-repeat', get_theme_mod('background_repeat', 'repeat')); ?> />
 <?php _e('No repeat') ?>
 </label>
 <label>
-<input name="background-repeat" type="radio" value="repeat" <?php checked('repeat', get_theme_mod('background_repeat')); ?> />
+<input name="background-repeat" type="radio" value="repeat" <?php checked('repeat', get_theme_mod('background_repeat', 'repeat')); ?> />
 <?php _e('Tile') ?>
 </label>
 </fieldset></td>
 
 <td><fieldset><legend class="screen-reader-text"><span><?php _e( 'Attachment' ); ?></span></legend>
 <label>
-<input name="background-attachment" type="radio" value="scroll" <?php checked('scroll', get_theme_mod('background_attachment')); ?> />
+<input name="background-attachment" type="radio" value="scroll" <?php checked('scroll', get_theme_mod('background_attachment', 'fixed')); ?> />
 <?php _e('Scroll') ?>
 </label>
 <label>
-<input name="background-attachment" type="radio" value="fixed" <?php checked('fixed', get_theme_mod('background_attachment')); ?> />
+<input name="background-attachment" type="radio" value="fixed" <?php checked('fixed', get_theme_mod('background_attachment', 'fixed')); ?> />
 <?php _e('Fixed') ?>
 </label>
 </fieldset></td>
diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index 0dfca9f1c8..f06e09e91a 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -1372,6 +1372,9 @@ function background_image() {
  * @param callback $admin_image_div_callback Output a custom background image div on the custom background administration screen. Optional.
  */
 function add_custom_background($header_callback = '', $admin_header_callback = '', $admin_image_div_callback = '') {
+	if ( isset($GLOBALS['custom_background']) )
+		return;
+
 	if ( empty($header_callback) )
 		$header_callback = '_custom_background_cb';
 
@@ -1397,19 +1400,19 @@ function _custom_background_cb() {
 	if ( !$background )
 		return;
 
-	$repeat = get_theme_mod('background_repeat');
+	$repeat = get_theme_mod('background_repeat', 'repeat');
 	if ( 'no-repeat' == $repeat )
 		$repeat = 'background-repeat: no-repeat;';
 	else
 		$repeat = 'background-repeat: repeat;';
-	$position = get_theme_mod('background_position');
+	$position = get_theme_mod('background_position', 'left');
 	if  ( 'center' == $position )
 		$position = 'background-position-x: center;';
 	elseif ( 'right' == $position )
 		$position = 'background-position-x: right;';
 	else
 		$position = 'background-position-x: left;';
-	$attachment = get_theme_mod('background_attachment');
+	$attachment = get_theme_mod('background_attachment', 'fixed');
 	if ( 'scroll' == $attachment )
 		$attachment = 'background-attachment: scroll;';
 	else