Index: wp-includes/class-wp-xmlrpc-server.php
===================================================================
--- wp-includes/class-wp-xmlrpc-server.php	(revision 17631)
+++ wp-includes/class-wp-xmlrpc-server.php	(working copy)
@@ -286,7 +286,7 @@
 	 * @since 2.6.0
 	 */
 	function initialise_blog_option_info( ) {
-		global $wp_version;
+		global $wp_version, $content_width;
 
 		$this->blog_options = array(
 			// Read only options
@@ -305,6 +305,11 @@
 				'readonly'		=> true,
 				'option'		=> 'siteurl'
 			),
+			'content_width'			=> array(
+				'desc'			=> __( 'Content Width' ),
+				'readonly'		=> true,
+				'value'			=> isset( $content_width ) ? (int) $content_width : 0,
+			),
 
 			// Updatable options
 			'time_zone'			=> array(