Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 17161)
+++ wp-includes/query.php	(working copy)
@@ -1559,6 +1559,9 @@
 		// Correct is_* for page_on_front and page_for_posts
 		if ( $this->is_home && 'page' == get_option('show_on_front') && get_option('page_on_front') ) {
 			$_query = wp_parse_args($query);
+			// pagename can be set and empty depending on matched rewrite rules. Ignore an empty pagename.
+			if ( isset($_query['pagename']) && '' == $_query['pagename'] )
+				unset($_query['pagename']);
 			if ( empty($_query) || !array_diff( array_keys($_query), array('preview', 'page', 'paged', 'cpage') ) ) {
 				$this->is_page = true;
 				$this->is_home = false;