Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 25568)
+++ wp-includes/functions.php	(working copy)
@@ -1622,7 +1622,10 @@
 	}
 
 	$basedir = $dir;
-	$baseurl = $url;
+	if ( is_ssl() )
+		$baseurl = str_replace( 'http://', 'https://', $url );
+	else
+		$baseurl = $url;
 
 	$subdir = '';
 	if ( get_option( 'uploads_use_yearmonth_folders' ) ) {