Index: shortcodes.php
===================================================================
--- shortcodes.php	(revision 19788)
+++ shortcodes.php	(working copy)
@@ -224,7 +224,7 @@
 
 	// allow [[foo]] syntax for escaping a tag
 	if ( $m[1] == '[' && $m[6] == ']' ) {
-		return substr($m[0], 1, -1);
+		return '['.substr($m[0], 2, -1);
 	}
 
 	$tag = $m[2];