diff --git a/mps/design/guide.impl.c.format.txt b/mps/design/guide.impl.c.format.txt
index fc2bb0ca20a..be4b522e307 100644
--- a/mps/design/guide.impl.c.format.txt
+++ b/mps/design/guide.impl.c.format.txt
@@ -5,6 +5,7 @@ C Style -- Formatting
 :Author: Richard Brooksby
 :Date: 1995-08-07
 :Status: complete guide
+:Format: rst
 :Revision: $Id$
 :Copyright: See `Copyright and License`_.