Index: wp-includes/classes.php
===================================================================
--- wp-includes/classes.php	(revision 12155)
+++ wp-includes/classes.php	(working copy)
@@ -450,16 +450,15 @@
  	 * Set the Headers for 404, if permalink is not found.
 	 *
 	 * Issue a 404 if a permalink request doesn't match any posts.  Don't issue
-	 * a 404 if one was already issued, if the request was a search, or if the
-	 * request was a regular query string request rather than a permalink
-	 * request. Issues a 200, if not 404.
+	 * a 404 if one was already issued or if the request was a search.
+	 * Issues a 200, if not 404.
 	 *
 	 * @since 2.0.0
  	 */
 	function handle_404() {
 		global $wp_query;
 
-		if ( (0 == count($wp_query->posts)) && !is_404() && !is_search() && ( $this->did_permalink || (!empty($_SERVER['QUERY_STRING']) && (false === strpos($_SERVER['REQUEST_URI'], '?'))) ) ) {
+		if ( 0 == count($wp_query->posts) && !is_404() && !is_search() ) {
 			// Don't 404 for these queries if they matched an object.
 			if ( ( is_tag() || is_category() || is_author() ) && $wp_query->get_queried_object() ) {
 				if ( !is_404() )