Index: wp-admin/custom-background.php
===================================================================
--- wp-admin/custom-background.php	(revision 22377)
+++ wp-admin/custom-background.php	(working copy)
@@ -212,8 +212,8 @@
 if ( get_background_image() ) {
 	// background-image URL must be single quote, see below
 	$background_styles .= ' background-image: url(\'' . set_url_scheme( get_theme_mod( 'background_image_thumb', get_background_image() ) ) . '\');'
-		. ' background-repeat: ' . get_theme_mod('background_repeat', 'repeat') . ';'
-		. ' background-position: top ' . get_theme_mod('background_position_x', 'left');
+		. ' background-repeat: ' . get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'background-repeat' ) ) . ';'
+		. ' background-position: top ' . get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'background-position' ) );
 }
 ?>
 <div id="custom-background-image" style="<?php echo $background_styles; ?>"><?php // must be double quote, see above ?>
@@ -286,15 +286,15 @@
 <th scope="row"><?php _e( 'Position' ); ?></th>
 <td><fieldset><legend class="screen-reader-text"><span><?php _e( 'Background Position' ); ?></span></legend>
 <label>
-<input name="background-position-x" type="radio" value="left"<?php checked('left', get_theme_mod('background_position_x', 'left')); ?> />
+<input name="background-position-x" type="radio" value="left"<?php checked( 'left', get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'background-position' ) ) ); ?> />
 <?php _e('Left') ?>
 </label>
 <label>
-<input name="background-position-x" type="radio" value="center"<?php checked('center', get_theme_mod('background_position_x', 'left')); ?> />
+<input name="background-position-x" type="radio" value="center"<?php checked( 'center', get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'background-position' ) ) ); ?> />
 <?php _e('Center') ?>
 </label>
 <label>
-<input name="background-position-x" type="radio" value="right"<?php checked('right', get_theme_mod('background_position_x', 'left')); ?> />
+<input name="background-position-x" type="radio" value="right"<?php checked( 'right', get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'background-position' ) ) ); ?> />
 <?php _e('Right') ?>
 </label>
 </fieldset></td>
@@ -303,10 +303,10 @@
 <tr valign="top">
 <th scope="row"><?php _e( 'Repeat' ); ?></th>
 <td><fieldset><legend class="screen-reader-text"><span><?php _e( 'Background Repeat' ); ?></span></legend>
-<label><input type="radio" name="background-repeat" value="no-repeat"<?php checked('no-repeat', get_theme_mod('background_repeat', 'repeat')); ?> /> <?php _e('No Repeat'); ?></label>
-	<label><input type="radio" name="background-repeat" value="repeat"<?php checked('repeat', get_theme_mod('background_repeat', 'repeat')); ?> /> <?php _e('Tile'); ?></label>
-	<label><input type="radio" name="background-repeat" value="repeat-x"<?php checked('repeat-x', get_theme_mod('background_repeat', 'repeat')); ?> /> <?php _e('Tile Horizontally'); ?></label>
-	<label><input type="radio" name="background-repeat" value="repeat-y"<?php checked('repeat-y', get_theme_mod('background_repeat', 'repeat')); ?> /> <?php _e('Tile Vertically'); ?></label>
+<label><input type="radio" name="background-repeat" value="no-repeat"<?php checked( 'no-repeat', get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'background-repeat' ) ) ); ?> /> <?php _e('No Repeat'); ?></label>
+	<label><input type="radio" name="background-repeat" value="repeat"<?php checked( 'repeat', get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'background-repeat' ) ) ); ?> /> <?php _e('Tile'); ?></label>
+	<label><input type="radio" name="background-repeat" value="repeat-x"<?php checked( 'repeat-x', get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'background-repeat' ) ) ); ?> /> <?php _e('Tile Horizontally'); ?></label>
+	<label><input type="radio" name="background-repeat" value="repeat-y"<?php checked( 'repeat-y', get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'background-repeat' ) ) ); ?> /> <?php _e('Tile Vertically'); ?></label>
 </fieldset></td>
 </tr>
 
@@ -314,11 +314,11 @@
 <th scope="row"><?php _e( 'Attachment' ); ?></th>
 <td><fieldset><legend class="screen-reader-text"><span><?php _e( 'Background Attachment' ); ?></span></legend>
 <label>
-<input name="background-attachment" type="radio" value="scroll" <?php checked('scroll', get_theme_mod('background_attachment', 'scroll')); ?> />
+<input name="background-attachment" type="radio" value="scroll" <?php checked( 'scroll', get_theme_mod( 'background_attachment', get_theme_support( 'custom-background', 'background-attachment' ) ) ); ?> />
 <?php _e('Scroll') ?>
 </label>
 <label>
-<input name="background-attachment" type="radio" value="fixed" <?php checked('fixed', get_theme_mod('background_attachment', 'scroll')); ?> />
+<input name="background-attachment" type="radio" value="fixed" <?php checked( 'fixed', get_theme_mod( 'background_attachment', get_theme_support( 'custom-background', 'background-attachment' ) ) ); ?> />
 <?php _e('Fixed') ?>
 </label>
 </fieldset></td>
Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 22377)
+++ wp-includes/theme.php	(working copy)
@@ -1134,17 +1134,17 @@
 	if ( $background ) {
 		$image = " background-image: url('$background');";
 
-		$repeat = get_theme_mod( 'background_repeat', 'repeat' );
+		$repeat = get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'background-repeat' ) );
 		if ( ! in_array( $repeat, array( 'no-repeat', 'repeat-x', 'repeat-y', 'repeat' ) ) )
 			$repeat = 'repeat';
 		$repeat = " background-repeat: $repeat;";
 
-		$position = get_theme_mod( 'background_position_x', 'left' );
+		$position = get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'background-position' ) );
 		if ( ! in_array( $position, array( 'center', 'right', 'left' ) ) )
 			$position = 'left';
 		$position = " background-position: top $position;";
 
-		$attachment = get_theme_mod( 'background_attachment', 'scroll' );
+		$attachment = get_theme_mod( 'background_attachment', get_theme_support( 'custom-background', 'background-attachment' ) );
 		if ( ! in_array( $attachment, array( 'fixed', 'scroll' ) ) )
 			$attachment = 'scroll';
 		$attachment = " background-attachment: $attachment;";
@@ -1322,10 +1322,13 @@
 				$args = array( 0 => array() );
 
 			$defaults = array(
-				'default-image' => '',
-				'default-color' => '',
-				'wp-head-callback' => '_custom_background_cb',
-				'admin-head-callback' => '',
+				'default-image'          => '',
+				'background-repeat'      => 'repeat',
+				'background-position'    => 'left',
+				'background-attachment'  => 'scroll',
+				'default-color'          => '',
+				'wp-head-callback'       => '_custom_background_cb',
+				'admin-head-callback'    => '',
 				'admin-preview-callback' => '',
 			);