Index: wp-admin/custom-header.php
===================================================================
--- wp-admin/custom-header.php	(revision 21018)
+++ wp-admin/custom-header.php	(working copy)
@@ -238,6 +238,7 @@
 		if ( isset( $_POST['removeheader'] ) ) {
 			check_admin_referer( 'custom-header-options', '_wpnonce-custom-header-options' );
 			set_theme_mod( 'header_image', 'remove-header' );
+			remove_theme_mod( 'header_image_data' );
 			return;
 		}