diff --git a/Lib/lib2to3/Grammar.txt b/Lib/lib2to3/Grammar.txt
index 8a96726..1e1f24c 100644
--- a/Lib/lib2to3/Grammar.txt
+++ b/Lib/lib2to3/Grammar.txt
@@ -1,4 +1,4 @@
-# Grammar for Python
+# Grammar for 2to3. This grammar supports Python 2.x and 3.x.
 
 # Note:  Changing the grammar specified in this file will most likely
 #        require corresponding changes in the parser module