diff --git a/Documentation/diff-format.txt b/Documentation/diff-format.txt
index 15c7e794f4..85b08909ce 100644
--- a/Documentation/diff-format.txt
+++ b/Documentation/diff-format.txt
@@ -66,7 +66,8 @@ be committed)
 
 Status letters C and R are always followed by a score (denoting the
 percentage of similarity between the source and target of the move or
-copy), and are the only ones to be so.
+copy).  Status letter M may be followed by a score (denoting the
+percentage of dissimilarity) for file rewrites.
 
 <sha1> is shown as all 0's if a file is new on the filesystem
 and it is out of sync with the index.