diff --git a/src/calibre/utils/filenames.py b/src/calibre/utils/filenames.py
index d9fd12d466..65451dab9c 100644
--- a/src/calibre/utils/filenames.py
+++ b/src/calibre/utils/filenames.py
@@ -229,6 +229,10 @@ def samefile(src, dst):
     symlinks, case insensitivity, mapped drives, etc.
 
     Returns True iff both paths exist and point to the same file on disk.
+
+    Note: On windows will return True if the two string are identical (upto
+    case) even if the file does not exist. This is because I have no way of
+    knowing how reliable the GetFileInformationByHandle method is.
     '''
     if iswindows:
         return samefile_windows(src, dst)