Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 23314)
+++ wp-includes/media.php	(working copy)
@@ -651,7 +651,7 @@
 
 	if ( $id ) $id = 'id="' . esc_attr($id) . '" ';
 
-	return '<div ' . $id . 'class="wp-caption ' . esc_attr($align) . '" style="width: ' . (10 + (int) $width) . 'px">'
+	return '<div ' . $id . 'class="wp-caption ' . esc_attr( $align ) . '" style="width: ' . apply_filters( 'wp-caption-width', ( 10 + (int) $width ) ) . 'px">'
 	. do_shortcode( $content ) . '<p class="wp-caption-text">' . $caption . '</p></div>';
 }