Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 17206)
+++ wp-includes/theme.php	(working copy)
@@ -1754,6 +1754,11 @@
 		$_wp_theme_features[$feature] = true;
 	else
 		$_wp_theme_features[$feature] = array_slice( func_get_args(), 1 );
+
+	if ( 'post-formats' == $feature && is_array( $_wp_theme_features[$feature][0] ) ) {
+		foreach ( array_keys( array_diff( $_wp_theme_features[$feature][0], get_post_format_slugs() ) ) as $key ) 
+			unset( $_wp_theme_features[$feature][0][$key] );
+	}
 }
 
 /**