Index: wp-includes/author-template.php
===================================================================
--- wp-includes/author-template.php	(revision 16337)
+++ wp-includes/author-template.php	(working copy)
@@ -232,7 +232,7 @@
 				$author_nicename = $user->user_nicename;
 		}
 		$link = str_replace('%author%', $author_nicename, $link);
-		$link = home_url() . trailingslashit($link);
+		$link = home_url( trailingslashit($link) );
 	}
 
 	$link = apply_filters('author_link', $link, $author_id, $author_nicename);