diff --git a/Lib/filecmp.py b/Lib/filecmp.py
index 7c47eb0..70a4b23 100644
--- a/Lib/filecmp.py
+++ b/Lib/filecmp.py
@@ -36,8 +36,9 @@ def cmp(f1, f2, shallow=True):
 
     f2 -- Second file name
 
-    shallow -- Just check stat signature (do not read the files).
-               defaults to True.
+    shallow -- treat files as identical if their stat signatures (type, size,
+               mtime) are identical. Otherwise, files are considered different
+               if their sizes or contents differ.  [default: True]
 
     Return value: