Index: wp-includes/canonical.php
===================================================================
--- wp-includes/canonical.php	(revision 22245)
+++ wp-includes/canonical.php	(working copy)
@@ -382,7 +382,7 @@
 
 	$compare_original = array($original['host'], $original['path']);
 
-	if ( !empty( $original['port'] ) )
+	if ( !empty( $original['port'] ) && 80 != $original['port'] )
 		$compare_original[] = $original['port'];
 
 	if ( !empty( $original['query'] ) )