diff --git a/README.md b/README.md
index feb0ba5baa42e2d2a21d1352188ede3f11366ae4..611c4c6201f95ab8dda9852cbff1c4630ade4f65 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,9 @@ in Galería:
 
 ```thumbs/2009/03/07/del-parque-guell-al-maremagnum```
 
+If the `Xmp.dc.subject` tag is missing, the photograph is asigned the album name
+of "Saturday 7" (for example), and therefore its directory will be `saturday-7`.
+
 The `Exif.Image.ImageDescription` tag is used for the comment or description of
 the photograph.