diff --git a/nw/project/document.py b/nw/project/document.py
index fa578dd4..36399353 100644
--- a/nw/project/document.py
+++ b/nw/project/document.py
@@ -20,7 +20,7 @@ logger = logging.getLogger(__name__)
 
 class NWDoc():
 
-    FILE_MN = "main.md"
+    FILE_MN = "main.nwd"
 
     def __init__(self, theProject):
 
diff --git a/sample/sampleNovel/data_6/36b6aa9b697b_main.md b/sample/sampleNovel/data_6/36b6aa9b697b_main.nwd
similarity index 100%
rename from sample/sampleNovel/data_6/36b6aa9b697b_main.md
rename to sample/sampleNovel/data_6/36b6aa9b697b_main.nwd
diff --git a/sample/sampleNovel/data_9/6b68994dfa3d_main.md b/sample/sampleNovel/data_9/6b68994dfa3d_main.nwd
similarity index 100%
rename from sample/sampleNovel/data_9/6b68994dfa3d_main.md
rename to sample/sampleNovel/data_9/6b68994dfa3d_main.nwd