Index: wp-includes/canonical.php
===================================================================
--- wp-includes/canonical.php	(revision 19872)
+++ wp-includes/canonical.php	(working copy)
@@ -92,6 +92,13 @@
 			}
 		}
 
+		if ( ! $redirect_url && get_option( 'home' ) != get_option( 'url' ) ) {
+			if ( $original['path'] == home_url( 'wp-admin/', 'relative' ) )
+				$redirect_url = admin_url();
+			elseif ( $original['path'] == home_url( 'wp-login.php', 'relative' ) )
+				$redirect_url = site_url( 'wp-login.php', 'login' );
+		}
+
 		if ( ! $redirect_url )
 			$redirect_url = redirect_guess_404_permalink( $requested_url );